> ## Documentation Index
> Fetch the complete documentation index at: https://v1-learn.neoartd.my.id/llms.txt
> Use this file to discover all available pages before exploring further.

# Functions

> 13 assignments

## 97. Picture Menu - [Link](https://programmingbydoing.com/a/picture-menu.html)

<Tabs>
  <Tab title="Task">
    In this program, you'll see how to call functions. Functions are chunks of code with a name, and "calling" a function means to call on the function to do a task for you.

    **Files Needed**

    * [PictureMenu.java](https://programmingbydoing.com/a/examples/PictureMenu.java)

    **Sample Output**

    ```bash theme={null}
    1. Butterfly
    2. Elephant
    3. Teddy Bear
    4. Snake

    Which animal to draw? 1
    ```
  </Tab>

  <Tab title="Code">
    ```java PictureMenu.java theme={null}
    import java.util.Scanner;

    public class PictureMenu
    {
        public static void main( String[] args )
        {
            Scanner kb = new Scanner(System.in);
            int choice;

            System.out.println( "1. Butterfly " );
            System.out.println( "2. Elephant  " );
            System.out.println( "3. Teddy Bear" );
            System.out.println( "4. Snake     " );

            System.out.print( "\nWhich animal to draw? " );
            choice = kb.nextInt();
            System.out.println();

            if ( choice == 1 )
            {
                butterfly();
            }
            else if ( choice == 2 )
            {
                elephant();
            }
            else if ( choice == 3 )
            {
                // * write code here to call the function named 'teddybear'
            }
            else if ( choice == 4 )
            {
                // * write code here to call the function named 'snake'
            }
            else
            {
                System.out.println( "Sorry, that wasn't one of the choices." );
            }

            System.out.println( "\nGoodbye!" );
        }

        public static void butterfly()
        {
            System.out.println("  .==-.                   .-==.     ");
            System.out.println("   \\()8`-._  `.   .'  _.-'8()/     ");
            System.out.println("   (88\"   ::.  \\./  .::   \"88)     ");
            System.out.println("    \\_.'`-::::.(#).::::-'`._/      ");
            System.out.println("      `._... .q(_)p. ..._.'         ");
            System.out.println("        \"\"-..-'|=|`-..-\"\"       ");
            System.out.println("        .\"\"' .'|=|`. `\"\".       ");
            System.out.println("      ,':8(o)./|=|\\.(o)8:`.        ");
            System.out.println("     (O :8 ::/ \\_/ \\:: 8: O)      ");
            System.out.println("      \\O `::/       \\::' O/       ");
            System.out.println("       \"\"--'         `--\"\"   hjw");
        }

        public static void elephant()
        {
            System.out.println("       _..--\"\"-.                  .-\"\"--.._ ");
            System.out.println("   _.-'         \\ __...----...__ /         '-._");
            System.out.println(" .'      .:::...,'              ',...:::.      '.");
            System.out.println("(     .'``'''::;                  ;::'''``'.     )");
            System.out.println(" \\             '-)              (-'             /");
            System.out.println("  \\             /                \\             /");
            System.out.println("   \\          .'.-.            .-.'.          /");
            System.out.println("    \\         | \\0|            |0/ |         /");
            System.out.println("    |          \\  |   .-==-.   |  /          |");
            System.out.println("     \\          `/`;          ;`\\`          /");
            System.out.println("      '.._      (_ |  .-==-.  | _)      _..'");
            System.out.println("          `\"`\"-`/ `/'        '\\` \\`-\"`\"`");
            System.out.println("               / /`;   .==.   ;`\\ \\");
            System.out.println("         .---./_/   \\  .==.  /   \\ \\");
            System.out.println("        / '.    `-.__)       |    `\"");
            System.out.println("       | =(`-.        '==.   ;");
            System.out.println(" jgs    \\  '. `-.           /");
            System.out.println("         \\_:_)   `\"--.....-'");
        }

        public static void teddybear()
        {
            System.out.println("            ___   .--. ");
            System.out.println("      .--.-\"   \"-' .- |");
            System.out.println("     / .-,`          .'");
            System.out.println("     \\   `           \\");
            System.out.println("      '.            ! \\");
            System.out.println("        |     !  .--.  |");
            System.out.println("        \\        '--'  /.____");
            System.out.println("       /`-.     \\__,'.'      `\\");
            System.out.println("    __/   \\`-.____.-' `\\      /");
            System.out.println("    | `---`'-'._/-`     \\----'    _");
            System.out.println("    |,-'`  /             |    _.-' `\\");
            System.out.println("   .'     /              |--'`     / |");
            System.out.println("  /      /\\              `         | |");
            System.out.println("  |   .\\/  \\      .--. __          \\ |");
            System.out.println("   '-'      '._       /  `\\         /");
            System.out.println("      jgs      `\\    '     |------'`");
            System.out.println("                 \\  |      |");
            System.out.println("                  \\        /");
            System.out.println("                   '._  _.'");
            System.out.println("                      ``");

        }

        public static void snake()
        {
            System.out.println("         ,,'6''-,.");
            System.out.println("        <====,.;;--.");
            System.out.println("        _`---===. \"\"\"==__");
            System.out.println("      //\"\"@@-\\===\\@@@@ \"\"\\\\");
            System.out.println("     |( @@@  |===|  @@@  ||");
            System.out.println("      \\\\ @@   |===|  @@  //");
            System.out.println("        \\\\ @@ |===|@@@ //");
            System.out.println("         \\\\  |===|  //");
            System.out.println("___________\\\\|===| //_____,----\"\"\"\"\"\"\"\"\"\"-----,_");
            System.out.println("  \"\"\"\"---,__`\\===`/ _________,---------,____    `,");
            System.out.println("             |==||                           `\\   \\");
            System.out.println("            |==| |          pb                 )   |");
            System.out.println("           |==| |       _____         ______,--'   '");
            System.out.println("           |=|  `----\"\"\"     `\"\"\"\"\"\"\"\"         _,-'");
            System.out.println("            `=\\     __,---\"\"\"-------------\"\"\"''");
            System.out.println("                \"\"\"\"		");
        }
    }
    ```
  </Tab>

  <Tab title="Question">
    Assignments turned in *without* these things will not receive any points.

    1. Add the two missing function calls for menu options 3 and 4.
       > Answer: Add `teddybear();` and `snake();` in the respective `else if` statements.
       ```java theme={null}
       else if ( choice == 3 )
       {
           teddybear();
       }
       else if ( choice == 4 )
       {
           snake();
       }
       ```
    2. Change the code in the if statement for choice 1 so that it calls the 'butterfly' function twice instead of just once. What happens now when you run the program and choose option 1? (Answer in a comment right underneath where you added the extra function call.)
       > Answer: Add `butterfly();` again in the respective `if` statement.
       ```java theme={null}
       if ( choice == 1 )
       {
           butterfly();
           butterfly(); // it will print the butterfly twice
       }
       ```
  </Tab>
</Tabs>

## 98. Flicker Phrase - [Link](https://programmingbydoing.com/a/flicker-phrase.html)

<Tabs>
  <Tab title="Task">
    Finish the program provided. You'll need to write five if statements and some function calls. If you do it right it should display a phrase in an interesting way.

    **Files Needed**

    * [FlickerPhrase.java](https://programmingbydoing.com/a/examples/FlickerPhrase.java)

    **Sample Output**

    ```bash theme={null}
    I pledge allegiance to the flag.
    ```
  </Tab>

  <Tab title="Code">
    ```java FlickerPhrase.java theme={null}
    import java.util.Random;

    public class FlickerPhrase
    {
        public static void main( String[] args )
        {
            Random rng = new Random();
            int r;

            for ( int i=0; i<100000; i++ )
            {
                r = 1 + rng.nextInt(5);
                // Write five if statements here.
                // If r is 1, then call the function named 'first'.
                // If r is 2, then call the function named 'second', and so on.

                // Optional: after the if statements are over, add in a slight delay.
            }

            System.out.println("I pledge allegiance to the flag.");
        }

        public static void first()
        {
            System.out.print("I                               \r");
        }

        public static void second()
        {
            System.out.print("  pledge                        \r");
        }

        public static void third()
        {
            System.out.print("         allegiance             \r");
        }

        public static void fourth()
        {
            System.out.print("                    to the      \r");
        }

        public static void fifth()
        {
            System.out.print("                           flag.\r");
        }
    }
    ```
  </Tab>

  <Tab title="Question">
    Assignments turned in *without* these things will not receive any points.

    1. Add the five if statements and function calls where indicated.
       > Answer: Add the following code in the `for` loop.
       ```java theme={null}
       if ( r == 1 )
       {
           first();
       }
       else if ( r == 2 )
       {
           second();
       }
       else if ( r == 3 )
       {
           third();
       }
       else if ( r == 4 )
       {
           fourth();
       }
       else if ( r == 5 )
       {
           fifth();
       }
       ```
    2. (optional) Add a delay using Thread.sleep()
       > Answer: Add the following code after the `if` statements.
       ```java theme={null}
       try
       {
           Thread.sleep(200);
       }
       catch ( InterruptedException e )
       {
           // do nothing
       }
       ```
  </Tab>
</Tabs>

## 99. Heron's Formula - [Link](https://programmingbydoing.com/a/herons-formula.html)

<Tabs>
  <Tab title="Task">
    In this program, you'll look at a function that "returns a value". When you call on the function to do a task, it will give you back a result.

    **Files Needed**

    * [HeronsFormula.java](https://programmingbydoing.com/a/examples/HeronsFormula.java)
    * [HeronsFormulaNoFunction.java](https://programmingbydoing.com/a/examples/HeronsFormulaNoFunction.java)

    **Sample Output**

    <CodeGroup>
      ```bash Before theme={null}
      A triangle with sides 3,3,3 has an area of 2.0
      A triangle with sides 3,4,5 has an area of 6.0
      A triangle with sides 7,8,9 has an area of 26.832815729997478
      A triangle with sides 5,12,13 has an area of 30.0
      A triangle with sides 10,9,11 has an area of 42.42640687119285
      A triangle with sides 8,15,17 has an area of 60.0
      ```

      ```bash After Everything Is Done theme={null}
      A triangle with sides 3,3,3 has an area of 3.897114317029974
      A triangle with sides 3,4,5 has an area of 6.0
      A triangle with sides 7,8,9 has an area of 26.832815729997478
      A triangle with sides 5,12,13 has an area of 30.0
      A triangle with sides 10,9,11 has an area of 42.42640687119285
      A triangle with sides 8,15,17 has an area of 60.0
      A triangle with sides 9,9,9 has an area of 35.074028853269766
      ```
    </CodeGroup>
  </Tab>

  <Tab title="Code">
    ```java HeronsFormula.java theme={null}
    public class HeronsFormula
    {
        public static void main( String[] args )
        {
            double a;

            a = triangleArea(3, 3, 3);
            System.out.println("A triangle with sides 3,3,3 has an area of " + a );

            a = triangleArea(3, 4, 5);
            System.out.println("A triangle with sides 3,4,5 has an area of " + a );

            a = triangleArea(7, 8, 9);
            System.out.println("A triangle with sides 7,8,9 has an area of " + a );

            System.out.println("A triangle with sides 5,12,13 has an area of " + triangleArea(5, 12, 13) );
            System.out.println("A triangle with sides 10,9,11 has an area of " + triangleArea(10, 9, 11) );
            System.out.println("A triangle with sides 8,15,17 has an area of " + triangleArea(8, 15, 17) );
        }

        public static double triangleArea( int a, int b, int c )
        {
            // the code in this function computes the area of a triangle whose sides have lengths a, b, and c
            double s, A;

            s = (a+b+c) / 2;
            A = Math.sqrt( s*(s-a)*(s-b)*(s-c) );

            return A;
            // ^ after computing the area, "return" it
        }
    }
    ```
  </Tab>

  <Tab title="Question">
    Assignments turned in *without* these things will not receive any points.

    1. Compile and run both files (HeronsFormula.java and HeronsFormulaNoFunction.java). Do they both produce the same output? (Answer in a comment in HeronsFormula.java.)
       > Answer: Yes, they both produce the same output.
    2. How many lines long is HeronsFormulaNoFunction.java? How many lines long is HeronsFormula.java if you don't count the two lines of comments inside the `triangleArea()` function? (Put the answers to both questions in a comment in HeronsFormula.java.)
       > Answer: HeronsFormulaNoFunction.java is 50 lines long. HeronsFormula.java is 32 lines long.
    3. There is a bug in the formula for both files. When `(a+b+c)` is an odd number, dividing by `2` throws away the `.5`. Fix both files so that instead of `(a+b+c) / 2` you have `(a+b+c) / 2.0` everywhere it occurs. Was it easier to fix the file that used a function, or the one that didn't use a function? Answer in a comment.
       > Answer: It was easier to fix the file that used a function.
       ```java HeronsFormula.java theme={null}
       s = (a+b+c) / 2.0;
       ```
       ```java HeronsFormulaNoFunction.java theme={null}
       s = (a+b+c) / 2.0;
       ```
    4. Add one more test to both files: find the area of a triangle with sides 9, 9, and 9. Was it difficult to add to the file that used a function? Answer in a comment on the line below where you added the new function call.
       > Answer: It was not difficult to add to the file that used a function.
       ```java HeronsFormula.java theme={null}
       System.out.println("A triangle with sides 9,9,9 has an area of " + triangleArea(9, 9, 9) );
       ```
    5. (You don't need to turn in HeronsFormulaNoFunction.java. Only turn in one file: HeronsFormula.java)
  </Tab>
</Tabs>

## 100. Distance Formula - [Link](https://programmingbydoing.com/a/distance-formula.html)

<Tabs>
  <Tab title="Task">
    Write a function to compute the distance between two points. Given two points (x1, y1) and (x2, y2), the distance between these points is given by the formula:
    ![Distance Formula](https://programmingbydoing.com/a/examples/distance_formula.gif)

    You must name the function `distance`, and it must return a `double` giving the distance between the two points.

    **Files Needed**

    * [DistanceFormula.java](https://programmingbydoing.com/a/examples/DistanceFormula.java)

    **Sample Output**

    ```bash theme={null}
    (-2,1) to (1,5) => 5.0
    (-2,-3) to (-4,4) => 7.280109889280518
    (2,-3) to (-1,-2) => 3.1622776601683795
    (4,5) to (4,5) => 0.0
    ```
  </Tab>

  <Tab title="Code">
    ```java DistanceFormula.java theme={null}
    public class DistanceFormula
    {
        public static void main( String[] args )
        {
            // test the formula a bit
            double d1 = distance(-2,1 , 1,5);
            System.out.println(" (-2,1) to (1,5) => " + d1 );

            double d2 = distance(-2,-3 , -4,4);
            System.out.println(" (-2,-3) to (-4,4) => " + d2 );

            System.out.println(" (2,-3) to (-1,-2) => " + distance(2,-3,-1,-2) );

            System.out.println(" (4,5) to (4,5) => " + distance(4,5,4,5) );
        }

        public static double distance( int x1, int y1, int x2, int y2 )
        {
            // put your code up in here
        }
    }
    ```
  </Tab>

  <Tab title="Answer">
    ```java DistanceFormula.java theme={null}
    public static double distance( int x1, int y1, int x2, int y2 )
    {
        return Math.sqrt( Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2) );
    }
    ```
  </Tab>
</Tabs>

## 101. Month Name - [Link](https://programmingbydoing.com/a/month-name.html)

<Tabs>
  <Tab title="Task">
    Write a function. It will return the name of a month of the year, given the month number, according to the table below. Make sure you **do not** put any input or output statements in the function; the month number will be *passed in* and the string containing the name will be *returned*.

    | Number        | Month     |
    | ------------- | --------- |
    | 1             | January   |
    | 2             | February  |
    | 3             | March     |
    | 4             | April     |
    | 5             | May       |
    | 6             | June      |
    | 7             | July      |
    | 8             | August    |
    | 9             | September |
    | 10            | October   |
    | 11            | November  |
    | 12            | December  |
    | anything else | error     |

    The function **must** be called `month_name()`, and must have one parameter (an integer), and return a `String`.

    And finally, here's some starter code.

    **Files Needed**

    * [MonthName.java](https://programmingbydoing.com/a/examples/MonthName.java)

    **Sample Output**

    ```bash theme={null}
    Month 1: January
    Month 2: February
    Month 3: March
    Month 4: April
    Month 5: May
    Month 6: June
    Month 7: July
    Month 8: August
    Month 9: September
    Month 10: October
    Month 11: November
    Month 12: December
    Month 43: error
    ```
  </Tab>

  <Tab title="Code">
    ```java MonthName.java theme={null}
    public class MonthName
    {
        public static String month_name( int month )
        {
            String result;
            // Your code goes in here.

            return result;
        }


        public static void main( String[] args )
        {
            System.out.println( "Month 1: " + month_name(1) );
            System.out.println( "Month 2: " + month_name(2) );
            System.out.println( "Month 3: " + month_name(3) );
            System.out.println( "Month 4: " + month_name(4) );
            System.out.println( "Month 5: " + month_name(5) );
            System.out.println( "Month 6: " + month_name(6) );
            System.out.println( "Month 7: " + month_name(7) );
            System.out.println( "Month 8: " + month_name(8) );
            System.out.println( "Month 9: " + month_name(9) );
            System.out.println( "Month 10: " + month_name(10) );
            System.out.println( "Month 11: " + month_name(11) );
            System.out.println( "Month 12: " + month_name(12) );
            System.out.println( "Month 43: " + month_name(43) );
        }
    }
    ```
  </Tab>

  <Tab title="Answer">
    ```java MonthName.java theme={null}
    public static String month_name( int month )
    {
        String result;
        if ( month == 1 )
        {
            result = "January";
        }
        else if ( month == 2 )
        {
            result = "February";
        }
        else if ( month == 3 )
        {
            result = "March";
        }
        else if ( month == 4 )
        {
            result = "April";
        }
        else if ( month == 5 )
        {
            result = "May";
        }
        else if ( month == 6 )
        {
            result = "June";
        }
        else if ( month == 7 )
        {
            result = "July";
        }
        else if ( month == 8 )
        {
            result = "August";
        }
        else if ( month == 9 )
        {
            result = "September";
        }
        else if ( month == 10 )
        {
            result = "October";
        }
        else if ( month == 11 )
        {
            result = "November";
        }
        else if ( month == 12 )
        {
            result = "December";
        }
        else
        {
            result = "error";
        }

        return result;
    }
    ```
  </Tab>
</Tabs>

## 102. Month Offset - [Link](https://programmingbydoing.com/a/month-offset.html)

<Tabs>
  <Tab title="Task">
    Write a function to give you the "month offset" given a number representing the month. You can get the month offset from the following table:

    | Month         | Month Offset |
    | ------------- | ------------ |
    | 1             | 1            |
    | 2             | 4            |
    | 3             | 4            |
    | 4             | 0            |
    | 5             | 2            |
    | 6             | 5            |
    | 7             | 0            |
    | 8             | 3            |
    | 9             | 6            |
    | 10            | 1            |
    | 11            | 4            |
    | 12            | 6            |
    | anything else | -1           |

    Of course, here's the main() to test your function.

    **Files Needed**

    * [MonthOffset.java](https://programmingbydoing.com/a/examples/MonthOffset.java)

    **Sample Output**

    ```bash theme={null}
    Offset for month 1: 1
    Offset for month 2: 4
    Offset for month 3: 4
    Offset for month 4: 0
    Offset for month 5: 2
    Offset for month 6: 5
    Offset for month 7: 0
    Offset for month 8: 3
    Offset for month 9: 6
    Offset for month 10: 1
    Offset for month 11: 4
    Offset for month 12: 6
    Offset for month 43: -1
    ```
  </Tab>

  <Tab title="Code">
    ```java MonthOffset.java theme={null}
    public class MonthOffset
    {
        public static int month_offset( int month )
        {
            int result;
            // Your code goes in here.

            return result;
        }

        public static void main( String[] args )
        {
            System.out.println( "Offset for month 1: " + month_offset(1) );
            System.out.println( "Offset for month 2: " + month_offset(2) );
            System.out.println( "Offset for month 3: " + month_offset(3) );
            System.out.println( "Offset for month 4: " + month_offset(4) );
            System.out.println( "Offset for month 5: " + month_offset(5) );
            System.out.println( "Offset for month 6: " + month_offset(6) );
            System.out.println( "Offset for month 7: " + month_offset(7) );
            System.out.println( "Offset for month 8: " + month_offset(8) );
            System.out.println( "Offset for month 9: " + month_offset(9) );
            System.out.println( "Offset for month 10: " + month_offset(10) );
            System.out.println( "Offset for month 11: " + month_offset(11) );
            System.out.println( "Offset for month 12: " + month_offset(12) );
            System.out.println( "Offset for month 43: " + month_offset(43) );
        }
    }
    ```
  </Tab>

  <Tab title="Answer">
    ```java MonthOffset.java theme={null}
    public static int month_offset( int month )
    {
        int result;
        if ( month == 1 )
        {
            result = 1;
        }
        else if ( month == 2 )
        {
            result = 4;
        }
        else if ( month == 3 )
        {
            result = 4;
        }
        else if ( month == 4 )
        {
            result = 0;
        }
        else if ( month == 5 )
        {
            result = 2;
        }
        else if ( month == 6 )
        {
            result = 5;
        }
        else if ( month == 7 )
        {
            result = 0;
        }
        else if ( month == 8 )
        {
            result = 3;
        }
        else if ( month == 9 )
        {
            result = 6;
        }
        else if ( month == 10 )
        {
            result = 1;
        }
        else if ( month == 11 )
        {
            result = 4;
        }
        else if ( month == 12 )
        {
            result = 6;
        }
        else
        {
            result = -1;
        }

        return result;
    }
    ```
  </Tab>
</Tabs>

## 103. Weekday Calculator - [Link](https://programmingbydoing.com/a/weekday-calculator.html)

<Tabs>
  <Tab title="Task">
    Using the functions you wrote in previous assignments and the leap year function provided, write a function to determine the day of the week a person was born given his or her birthday. The following steps should be used to find the day of the week corresponding to any date from 1901 through the present.

    In the following explanation, the following terms will be helpful. Assuming I type in my birthday as "6 10 1981":

    The *month* is 6.
    The *day of the month* is 10.
    The *year* is 1981.

    1. Find the number of years since 1900, and put it into a variable called `yy`. Simply subtract 1900 from the year to get this.
    2. Divide the number of years since 1900 by 4. Put the quotient in a variable called `total`. For example, if the person was born in 1983, divide 83 by 4 and store 20 in `total`.
    3. Also add the number of years since 1900 to `total`.
    4. Add the day of the month to `total`.
    5. Using the function `month_offset()` you wrote, find the "month offset" and add it to `total`.
    6. If the year is a leap year and if the month you are working with is either January or February, then subtract 1 from the `total`. You can use the function `is_leap()` provided to determine if the year is a leap year.
    7. Find the remainder when `total` is divided by 7. Pass this remainder to the function `weekday_name()` you wrote to determine the day of the week the person was born.
    8. Finally, build up a single String value containing the whole date (day of week, month, day, year). You'll need to use the function `month_name()` you wrote to show the month name rather than its number.
    9. Return that String value.

    Whew. Here's some code to get you started.

    **Files Needed**

    * [WeekdayCalculator.java](https://programmingbydoing.com/a/examples/WeekdayCalculator.java)

    **Sample Output**

    ```bash theme={null}
    Welcome to Mr. Mitchell's fantastic birth-o-meter!

    All you have to do is enter your birthday, and it will tell you
    the day of the week on which you were born.

    Some automatic tests....
    12 10 2003 => Wednesday, December 10, 2003
     2 13 1976 => Friday, February 13, 1976
     2 13 1977 => Sunday, February 13, 1977
     7  2 1974 => Tuesday, July 2, 1974
     1 15 2003 => Wednesday, January 15, 2003
    10 13 2000 => Friday, October 13, 2000

    Now it's your turn!  What's your birthday?
    Birthday (mm dd yyyy): 11 11 2010

    You were born on Thursday, November 11, 2010!
    ```
  </Tab>

  <Tab title="Code">
    ```java WeekdayCalculator.java theme={null}
    import java.util.Scanner;

    public class WeekdayCalculator
    {
        public static void main( String[] args )
        {
            Scanner keyboard = new Scanner(System.in);

            System.out.println("Welcome to Mr. Mitchell's fantastic birth-o-meter!");
            System.out.println();
            System.out.println("All you have to do is enter your birth date, and it will");
            System.out.println("tell you the day of the week on which you were born.");
            System.out.println();
            System.out.println("Some automatic tests....");
            System.out.println("12 10 2003 => " + weekday(12,10,2003));
            System.out.println(" 2 13 1976 => " + weekday(2,13,1976));
            System.out.println(" 2 13 1977 => " + weekday(2,13,1977));
            System.out.println(" 7  2 1974 => " + weekday(7,2,1974));
            System.out.println(" 1 15 2003 => " + weekday(1,15,2003));
            System.out.println("10 13 2000 => " + weekday(10,13,2000));
            System.out.println();

            System.out.println("Now it's your turn!  What's your birthday?");
            System.out.print("Birth date (mm dd yyyy): ");
            int mm = keyboard.nextInt();
            int dd = keyboard.nextInt();
            int yyyy = keyboard.nextInt();

            // put a function call for weekday() here
            System.out.println("You were born on ");
        }

        public static String weekday( int mm, int dd, int yyyy )
        {
            int yy, total;
            String date = "";

            // bunch of calculations go here

            date = month_name(mm) + ", " + yyyy;

            return date;
        }

        // paste your functions from MonthName, WeekdayName, and MonthOffset here

        public static boolean is_leap( int year )
        {
            // years which are evenly divisible by 4 are leap years,
            // but years divisible by 100 are not leap years,
            // though years divisible by 400 are leap years
            boolean result;

            if ( year%400 == 0 )
                result = true;
            else if ( year%100 == 0 )
                result = false;
            else if ( year%4 == 0 )
                result = true;
            else
                result = false;

            return result;
        }
    }
    ```
  </Tab>

  <Tab title="Answer">
    ```java WeekdayCalculator.java theme={null}
    public static String weekday( int mm, int dd, int yyyy )
    {
        int yy, total;
        String date = "";

        yy = yyyy - 1900;
        total = yy / 4;
        total += yy;
        total += dd;
        total += month_offset(mm);
        if ( is_leap(yyyy) && (mm == 1 || mm == 2) )
        {
            total -= 1;
        }

        date = weekday_name(total % 7) + ", " + month_name(mm) + " " + dd + ", " + yyyy;

        return date;
    }

    public static String weekday_name( int weekday )
    {
        String result = "";

        if ( weekday == 1 )
        {
            result = "Sunday";
        }
        else if ( weekday == 2 )
        {
            result = "Monday";
        }
        else if ( weekday == 3 )
        {
            result = "Tuesday";
        }
        else if ( weekday == 4 )
        {
            result = "Wednesday";
        }
        else if ( weekday == 5 )
        {
            result = "Thursday";
        }
        else if ( weekday == 6 )
        {
            result = "Friday";
        }
        else if ( weekday == 0 )
        {
            result = "Saturday";
        }
        else
        {
            result = "error";
        }

        return result;
    }

    public static int month_offset( int month )
    {
        int result;

        if ( month == 1 )
        {
            result = 1;
        }
        else if ( month == 2 )
        {
            result = 4;
        }
        else if ( month == 3 )
        {
            result = 4;
        }
        else if ( month == 4 )
        {
            result = 0;
        }
        else if ( month == 5 )
        {
            result = 2;
        }
        else if ( month == 6 )
        {
            result = 5;
        }
        else if ( month == 7 )
        {
            result = 0;
        }
        else if ( month == 8 )
        {
            result = 3;
        }
        else if ( month == 9 )
        {
            result = 6;
        }
        else if ( month == 10 )
        {
            result = 1;
        }
        else if ( month == 11 )
        {
            result = 4;
        }
        else if ( month == 12 )
        {
            result = 6;
        }
        else
        {
            result = -1;
        }

        return result;
    }

    public static String month_name( int month )
    {
        String result;

        if ( month == 1 )
        {
            result = "January";
        }
        else if ( month == 2 )
        {
            result = "February";
        }
        else if ( month == 3 )
        {
            result = "March";
        }
        else if ( month == 4 )
        {
            result = "April";
        }
        else if ( month == 5 )
        {
            result = "May";
        }
        else if ( month == 6 )
        {
            result = "June";
        }
        else if ( month == 7 )
        {
            result = "July";
        }
        else if ( month == 8 )
        {
            result = "August";
        }
        else if ( month == 9 )
        {
            result = "September";
        }
        else if ( month == 10 )
        {
            result = "October";
        }
        else if ( month == 11 )
        {
            result = "November";
        }
        else if ( month == 12 )
        {
            result = "December";
        }
        else
        {
            result = "error";
        }

        return result;
    }

    public static boolean is_leap( int year )
    {
        boolean result;

        if ( year%400 == 0 )
            result = true;
        else if ( year%100 == 0 )
            result = false;
        else if ( year%4 == 0 )
            result = true;
        else
            result = false;

        return result;
    }
    ```
  </Tab>
</Tabs>

## 104. Area Calculator - [Link](https://programmingbydoing.com/a/area-calculator.html)

<Tabs>
  <Tab title="Task">
    Write a program to calculate the area of four different geometric shapes: triangles, squares, rectangles, and circles. You must use functions. Here are the functions you should create:

    ```java theme={null}
    public static double area_circle( int radius )              // returns the area of a circle
    public static int area_rectangle( int length, int width )   // returns the area of a rectangle
    public static int area_square( int side )                   // returns the area of a square
    public static double area_triangle( int base, int height )  // returns the area of a triangle
    ```

    Your program should present a menu for the human to choose which shape to calculate, then ask them for the appropriate values (length, width, radius, etc.). Then it should pass those values to the appropriate function and display the resulting area.

    Notice that you *must not* input the values inside the functions, and you *must not* display the values inside the functions. *All* input and output must be in the `main()`, and values must be passed to the functions and returned from them.

    | Shape     | Formula                     |
    | --------- | --------------------------- |
    | square    | $A = s^2$                   |
    | rectangle | $A = l \times w$            |
    | triangle  | $A = \frac{1}{2} \times bh$ |
    | circle    | $A = \pi r^2$               |

    You'll need the value of $\pi$ for `area_circle();` feel free to use the built-in `double` variable called `Math.PI`.

    The menu should keep looping until the human chooses to quit.

    **Sample Output**

    ```bash theme={null}
    Shape Area Calculator version 0.1 (c) 2005 Mitchell Sample Output, Inc.

    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    1) Triangle
    2) Rectangle
    3) Square
    4) Circle
    5) Quit
    Which shape: 1

    Base: 5
    Height: 6

    The area is 15.

    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    1) Triangle
    2) Rectangle
    3) Square
    4) Circle
    5) Quit
    Which shape: 2

    Length: 10
    Width: 4

    The area is 40.

    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    1) Triangle
    2) Rectangle
    3) Square
    4) Circle
    5) Quit
    Which shape: 3

    Side length: 9

    The area is 81.

    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    1) Triangle
    2) Rectangle
    3) Square
    4) Circle
    5) Quit
    Which shape: 4

    Radius: 4

    The area is 50.2655.

    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    1) Triangle
    2) Rectangle
    3) Square
    4) Circle
    5) Quit
    Which shape: 5

    Goodbye.
    ```
  </Tab>

  <Tab title="Code">
    ```java AreaCalculator.java theme={null}
    import java.util.Scanner;

    public class AreaCalculator
    {
        public static void main( String[] args )
        {
            Scanner keyboard = new Scanner(System.in);

            System.out.println("Shape Area Calculator version 0.1 (c) 2005 Mitchell Sample Output, Inc.");

            int choice;
            do
            {
                System.out.println("\n-=-=-=-=-=-=-=-=-=-=-=-=-=-\n");
                System.out.println("1) Triangle");
                System.out.println("2) Rectangle");
                System.out.println("3) Square");
                System.out.println("4) Circle");
                System.out.println("5) Quit");
                System.out.print("Which shape: ");
                choice = keyboard.nextInt();

                if ( choice == 1 )
                {
                    System.out.print("\nBase: ");
                    int base = keyboard.nextInt();
                    System.out.print("Height: ");
                    int height = keyboard.nextInt();
                    System.out.printf("\nThe area is %s.\n", area_triangle(base, height));
                }
                else if ( choice == 2 )
                {
                    System.out.print("\nLength: ");
                    int length = keyboard.nextInt();
                    System.out.print("Width: ");
                    int width = keyboard.nextInt();
                    System.out.printf("\nThe area is %s.\n", area_rectangle(length, width));
                }
                else if ( choice == 3 )
                {
                    System.out.print("\nSide length: ");
                    int side = keyboard.nextInt();
                    System.out.printf("\nThe area is %s.\n", area_square(side));
                }
                else if ( choice == 4 )
                {
                    System.out.print("\nRadius: ");
                    int radius = keyboard.nextInt();
                    System.out.printf("\nThe area is %.4s.\n", area_circle(radius));
                }
            } while ( choice != 5 );

            System.out.println("\nGoodbye.");
        }

        public static double area_circle( int radius )
        {
            return Math.PI * Math.pow(radius, 2);
        }

        public static int area_rectangle( int length, int width )
        {
            return length * width;
        }

        public static int area_square( int side )
        {
            return (int) Math.pow(side, 2);
        }

        public static int area_triangle( int base, int height )
        {
            return (int) (0.5 * base * height);
        }
    }
    ```
  </Tab>
</Tabs>

## 105. Function Call Alphabet - [Link](https://programmingbydoing.com/a/function-call-alphabet.html)

<Tabs>
  <Tab title="Task">
    Download and finish the following code to practice writing function calls.

    **Files Needed**

    * [FunctionCallAlphabet.java](https://programmingbydoing.com/a/examples/FunctionCallAlphabet.java)

    **Sample Output**

    ```bash theme={null}
    Ant Banana Crocodile Doggie Elephant Frog Gorilla Horseradish
    Ice_cream Jackrabbit Kiwi Lhasa_apso Monkey! Narwhal Orangutan Parrot Quail
    Rabbit Snake Thyme Ugli_fruit Valentine_candy Walrus X_men Yams Zebra
    ```

    <Note>
      Note that this exercise only requires you to write function calls. The function implementations are already complete. If you do everything correctly, it should produce output like the following:
    </Note>
  </Tab>

  <Tab title="Code">
    ```java FunctionCallAlphabet.java theme={null}
    // Function Call Alphabet - Yet another program to practice functions, but this time it's function calls only.

    public class FunctionCallAlphabet
    {
        public static void main( String[] args )
        {
            // ???? a( ???? );    // displays a word beginning with A
            // ???? b( ???? );    // returns the word to be displayed
            // ???? c( ???? );    // pass it 'true' and it will display a word beginning with C
            // ???? d( ???? );    // displays a word beginning with D
            // ???? e( ???? );    // pass it the number of letters to display (9)
            // ???? f( ???? );    // displays the word you pass it beginning with "F"
            // ???? g( ???? );    // returns the word to be displayed
            // ???? h( ???? );    // tell it how many times to display the word (1)
            System.out.println();

            // ???? i( ???? );    // pass it any integer and it will display a word beginning with I
            // ???? j( ???? );    // returns a different word depending on what you pass it (1-3)
            // ???? k( ???? );    // displays a word beginning with K
            // ???? l( ???? );    // displays a different word depending on the two booleans you pass it
            // ???? m( ???? );    // displays a different word depending on the two booleans you pass it
            // ???? n( ???? );    // displays the word you pass it beginning with "N"
            // ???? o( ???? );    // displays a word beginning with O and returns a useless value
            // ???? p( ???? );    // returns the word to be displayed
            // ???? q( ???? );    // displays the word
            System.out.println();

            // ???? r( ???? );    // returns a different word depending on if you pass it 'true' or 'false'
            // ???? s( ???? );    // pass it the number of letters to display (6)
            // ???? t( ???? );    // displays the word you pass it beginning with "T"
            // ???? u( ???? );    // returns the word to be displayed
            // ???? v( ???? );    // tell it how many times to display the word (1)
            // ???? w( ???? );    // pass it any integer and it will display a word beginning with W
            // ???? x( ???? );    // returns a different word depending on what you pass it (1-2)
            // ???? y( ???? );    // displays a word beginning with Y
            // ???? z( ???? );    // returns a different word depending on which two boolean values you pass it
            System.out.println();
        }

        /**************************************
        * Don't change anything below here!! *
        *************************************/

        public static void a()
        {
            System.out.print("Ant ");
        }

        public static String b()
        {
            return "Banana ";
        }

        public static void c(boolean doit)
        {
            if ( doit )
                System.out.print("Crocodile ");
        }

        public static void d()
        {
            System.out.print("Doggie ");
        }

        public static void e(int howmany)
        {
            String s;
            s = "Elephant ";
            int x = 0;
            while ( x < howmany )
            {
                System.out.print( s.charAt(x) );
                x = x+1;
            }

        }

        public static void f(String word)
        {
            System.out.print(word + " ");
        }

        public static String g()
        {
            return "Gorilla ";
        }

        public static void h(int reps)
        {
            int x = 0;
            while ( x < reps )
            {
                System.out.print("Horseradish ");
                x = x+1;
            }

        }

        public static void i(int ignoredparameter)
        {
            ignoredparameter = 32;
            String space = Character.toString( (char) ignoredparameter );
            System.out.print("Ice_cream" + space);
        }

        public static String j(int whichone)
        {
            if ( whichone == 1 )
                return "Jambalaya ";
            else if ( whichone == 2 )
                return "Juniper ";
            else
                return "Jackrabbit ";
        }

        public static void k()
        {
            // the bird OR the fruit
            System.out.print("Kiwi ");
        }

        public static void l(boolean a, boolean b)
        {
            if ( a && b )
                System.out.print("Lettuce ");
            else
                System.out.print("Lhasa_apso ");
        }

        public static void m(boolean a, boolean b)
        {
            if ( a || b )
                System.out.print("Mango ");
            else
                System.out.print("Monkey! ");
        }

        public static void n(String word)
        {
            System.out.print(word + " ");
        }

        public static int o()
        {
            System.out.print("Orangutan ");
            return 1;	// just for kicks; the return value doesn't mean anything
        }

        public static String p()
        {
            return "Parrot ";
        }

        public static void q()
        {
            System.out.print("Quail ");
        }

        public static String r(boolean first)
        {
            if ( first )
                return "Rabbit ";
            else
                return "Radish ";
        }

        public static void s(int howmany)
        {
            String s;
            s = "Snake ";
            int x = 0;
            while ( x < howmany )
            {
                System.out.print( s.charAt(x) );
                x = x+1;
            }
        }

        public static void t(String word)
        {
            System.out.print(word + " ");
        }

        public static String u()
        {
            return "Ugli_fruit ";
        }

        public static void v(int reps)
        {
            int x = 0;
            while ( x < reps )
            {
                System.out.print("Valentine_candy ");
                x = x+1;
            }
        }

        public static void w(int ignoredparameter)
        {
            ignoredparameter = 32;
            String space = Character.toString( (char) ignoredparameter );
            System.out.print("Walrus" + space);
        }

        public static String x(int whichone)
        {
            if ( whichone == 1 )
                return "X_files ";
            else
                return "X_men ";
        }

        public static void y()
        {
            System.out.print("Yams ");
        }

        public static String z(boolean a, boolean b)
        {
            if ( a || b )
                return "Zanahorias ";
            else
                return "Zebra ";
        }
    }
    ```
  </Tab>

  <Tab title="Answer">
    ```java FunctionCallAlphabet.java theme={null}
    public static void main( String[] args )
    {
        a();
        System.out.print( b() );
        c(true);
        d();
        e(9);
        f("Frog ");
        System.out.print( g() );
        h(1);
        System.out.println();

        i(32);
        System.out.print( j(3) );
        k();
        l(true, false);
        m(false, false);
        n("Narwhal ");
        o();
        System.out.print( p() );
        q();
        System.out.println();

        System.out.print( r(true) );
        s(6);
        t("Thyme ");
        System.out.print( u() );
        v(1);
        w(32);
        System.out.print( x(2) );
        y();
        System.out.print( z(true, false) );
        System.out.println();
    }
    ```
  </Tab>
</Tabs>

## 106. Fill-In Functions - [Link](https://programmingbydoing.com/a/fill-in-functions.html)

<Tabs>
  <Tab title="Task">
    Download and finish the following code to practice working with functions:

    **Files Needed**

    * [FillInFunctions.java](https://programmingbydoing.com/a/examples/FillInFunctions.java)

    If you do everything correctly, it should produce output like the following:

    **Sample Output**

    ```bash theme={null}
    Watch as we demonstrate functions.

    I'm going to get a random character from A-Z
    The character is: N (or whatever)

    Now let's count from -10 to 10
    -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 How was that?

    Now we take the absolute value of a number.
    |-10| = 10

    That's all.  This program has been brought to you by:

    programmed by Graham Mitchell
    modified by [your name here]
    This code is distributed under the terms of the standard BSD license.  Do with i
    t as you wish.
    ```
  </Tab>

  <Tab title="Code">
    ```java FillInFunctions.java theme={null}
    // Fill-In Functions - Fix the broken functions and function calls.

    public class FillInFunctions
    {
        public static void main( String[] args )
        {
            // Fill in the function calls where appropriate.

            System.out.println("Watch as we demonstrate functions.");

            System.out.println();
            System.out.println("I'm going to get a random character from A-Z");
            char c = '!';
            // randchar();
            System.out.println("The character is: " + c );

            System.out.println();
            System.out.println("Now let's count from -10 to 10");
            int begin, end;
            begin = -10;
            end = 10;
            // counter();
            System.out.println("How was that?");

            System.out.println();
            System.out.println("Now we take the absolute value of a number.");
            int x, y = 99;
            x = -10;
            // abso();
            System.out.println("|" + x + "| = " + y );

            System.out.println();
            System.out.println("That's all.  This program has been brought to you by:");
            // credits();
        }

    /*
        public static ???? credits( ???? )
        // No parameters.
        {
            // displays some boilerplate text saying who wrote this program, etc.

            System.out.println();
            System.out.println("programmed by Graham Mitchell");
            System.out.println("modified by [your name here]");
            System.out.print("This code is distributed under the terms of the standard ");
            System.out.println("BSD license.  Do with it as you wish.");

            return ??;
        }
    */

    /*
        public static ???? randchar( ???? )
        // No parameters.
        {
            // chooses a random character in the range "A" to "Z"

            int numval;
            char charval;

            // pick a random number from 0 to 25
            numval = (int)(Math.random()*26);
            // now add that offset to the value of the letter 'A'
            charval = (char) ('A' + numval);

            return ??;
        }
    */

    /*
        public static ???? counter( ???? )
        // Parameters are:
        //     int start;
        //     int stop;
        {
            // counts from start to stop by ones
            int ctr;

            ctr = start;
            while ( ctr <= stop )
            {
                System.out.print(ctr + " ");
                ctr = ctr+1;
            }

            return ??;
        }
    */

    /*
        public static ???? abso( ???? )
        // Parameters are:
        //     int value;
        {
            // finds the absolute value of the parameter
            int absval;

            if ( value < 0 )
                absval = -value;
            else
                absval = value;

            return ??;
        }
    */

    }
    ```
  </Tab>

  <Tab title="Answer">
    ```java FillInFunctions.java theme={null}
    public static void main( String[] args )
    {
        // Fill in the function calls where appropriate.

        System.out.println("Watch as we demonstrate functions.");

        System.out.println();
        System.out.println("I'm going to get a random character from A-Z");
        char c = '!';
        c = randchar();
        System.out.println("The character is: " + c );

        System.out.println();
        System.out.println("Now let's count from -10 to 10");
        int begin, end;
        begin = -10;
        end = 10;
        counter(begin, end);
        System.out.println("How was that?");

        System.out.println();
        System.out.println("Now we take the absolute value of a number.");
        int x, y = 99;
        x = -10;
        y = abso(x);
        System.out.println("|" + x + "| = " + y );

        System.out.println();
        System.out.println("That's all.  This program has been brought to you by:");
        credits();
    }

    public static void credits()
    // No parameters.
    {
        // displays some boilerplate text saying who wrote this program, etc.

        System.out.println();
        System.out.println("programmed by Graham Mitchell");
        System.out.println("modified by [your name here]");
        System.out.print("This code is distributed under the terms of the standard ");
        System.out.println("BSD license.  Do with it as you wish.");
    }

    public static char randchar()
    // No parameters.
    {
        // chooses a random character in the range "A" to "Z"

        int numval;
        char charval;

        // pick a random number from 0 to 25
        numval = (int)(Math.random()*26);
        // now add that offset to the value of the letter 'A'
        charval = (char) ('A' + numval);

        return charval;
    }

    public static void counter( int start, int stop )
    // Parameters are:
    //     int start;
    //     int stop;
    {
        // counts from start to stop by ones
        int ctr;

        ctr = start;
        while ( ctr <= stop )
        {
            System.out.print(ctr + " ");
            ctr = ctr+1;
        }
    }

    public static int abso( int value )
    // Parameters are:
    //     int value;
    {
        // finds the absolute value of the parameter
        int absval;

        if ( value < 0 )
            absval = -value;
        else
            absval = value;

        return absval;
    }
    ```
  </Tab>
</Tabs>

## 107. More Fill-In Functions - [Link](https://programmingbydoing.com/a/more-fill-in-functions.html)

<Tabs>
  <Tab title="Task">
    Download and finish the following code to practice working with functions:

    **Files Needed**

    * [MoreFillInFunctions.java](https://programmingbydoing.com/a/examples/MoreFillInFunctions.java)

    If you do everything correctly, it should produce output like the following:

    **Sample Output**

    ```bash theme={null}
    Here we go.

    Some random numbers, if you please:
    First: 2
    Second: 8
    They were not the same.

    More counting, but this time not by ones: 2 4 6 8 10 8 6 4 2
    Let's figure a project grade.
    434521 -> 71

    Finally, some easy ones.Please enter your name: jose
    Hi, jose

    Do you feel lucky, punk?
    you lose
    ```
  </Tab>

  <Tab title="Code">
    ```java MoreFillInFunctions.java theme={null}
    // More Fill-In Functions - Fix the broken functions and function calls (again).

    import java.util.Scanner;

    public class MoreFillInFunctions
    {
        public static void main( String[] args )
        {
            // Fill in the function calls where indicated.
            System.out.println("Here we go.");

            System.out.println();
            System.out.println("Some random numbers, if you please: ");
            int lo, hi, val1 = 999, val2 = 999;
            lo = 1;
            hi = 10;
            // superrand();
            System.out.println("First: " + val1 );
            // superrand();  // this time, put hi first
            System.out.println("Second: " + val2 );
            if ( val1 == val2 )
                System.out.println("Hey!  They were the same!");
            else
                System.out.println("They were not the same.");

            System.out.println();
            System.out.print("More counting, but this time not by ones: ");
            // count from 2 to 8 by 2s
            // stepcount();
            // count from 10 to 2 by 2s
            // stepcount();

            System.out.println();
            System.out.println("Let's figure a project grade.");
            int a=4,b=3,c=4,d=5,e=2,f=1, result=999;
            // project_grade();
            System.out.println("434521 -> " + result );

            System.out.println();
            System.out.print("Finally, some easy ones.");

            String nombre = "ERROR";
            // get_name();
            System.out.println("Hi, " + nombre );

            System.out.println();
            System.out.println("Do you feel lucky, punk?");
            // crash();
            System.out.println();
        }

    /*
        public static ???? superrand( ???? )
        // Parameters are:
        //	int a;
        //	int b;
        {
            // picks a number between a and b, no matter which is larger
            int c;

            if ( a < b )	// b is larger
                c = a + (int)(Math.random()*(b-a+1));
            else if ( a > b )	// a is larger
                c = b + (int)(Math.random()*(a-b+1));
            else
                c = a;	// or c = b; doesn't matter since they're equal

            return ??;
        }
    */

    /*
        public static ???? stepcount( ???? )
        // Parameters are:
        //     int first;
        //     int last;
        //     int step;
        {
            // counts from 'first' to 'last' by 'step'
            // handles forward and backward
            int x;

            if ( first < last )
            {
                x = first;
                while ( x <= last )
                {
                    System.out.print(x + " ");
                    x = x + step;
                }
            }
            else
            {
                x = first;
                while ( x >= last )
                {
                    System.out.print(x + " ");
                    x = x - step;
                }
            }

            return ??;
        }
    */

    /*
        public static ???? project_grade( ???? )
        // Parameters are:
        //     int p1, p2, p3, p4, p5, p6;
        {
            // given six integers representing scores out of five in each of the
            // six categories for the first six weeks project: tells you your
            // overall project grade out of 100

            int overall_grade;

            overall_grade = p1 * 6;    // six points per point for the first category
            overall_grade = overall_grade + ( p2 * 6 );   // six points per point
            overall_grade = overall_grade + ( p3 * 4 );   // four points per point
            overall_grade = overall_grade + ( p4 * 2 );   // two points per point
            overall_grade = overall_grade + ( p5 * 1 );   // one point per point
            overall_grade = overall_grade + ( p6 * 1 );   // one point per point

            return ??;
        }
    */

    /*
        public static ???? get_name( ???? )
        // No parameters.
        {
            // finds out the user's name
            Scanner keyboard = new Scanner(System.in);

            String name;
            System.out.print("Please enter your name: ");
            name = keyboard.next();

            return ??;
        }
    */

    /*
        public static ???? crash( ???? )
        // No parameters.
        {
            // displays "you win" or "you lose".  You lose 90% of the time.
            String magic_word;

            if ( (int)(Math.random()*10) == 0 )
            {
                // What do you know?  We won!
                magic_word = "win";
            }
            else
            {
                // No big suprise; we lost.
                magic_word = "lose";
            }

            System.out.print("you " + magic_word);

            return ??;
        }
    */
    }
    ```
  </Tab>

  <Tab title="Answer">
    ```java MoreFillInFunctions.java theme={null}
    public static void main( String[] args )
    {
        // Fill in the function calls where indicated.
        System.out.println("Here we go.");

        System.out.println();
        System.out.println("Some random numbers, if you please: ");
        int lo, hi, val1 = 999, val2 = 999;
        lo = 1;
        hi = 10;
        val1 = superrand(lo, hi);
        System.out.println("First: " + val1 );
        val2 = superrand(hi, lo);
        System.out.println("Second: " + val2 );
        if ( val1 == val2 )
            System.out.println("Hey!  They were the same!");
        else
            System.out.println("They were not the same.");

        System.out.println();
        System.out.print("More counting, but this time not by ones: ");
        // count from 2 to 8 by 2s
        stepcount(2, 8, 2);
        // count from 10 to 2 by 2s
        stepcount(10, 2, 2);

        System.out.println();
        System.out.println("Let's figure a project grade.");
        int a=4,b=3,c=4,d=5,e=2,f=1, result=999;
        result = project_grade(a, b, c, d, e, f);
        System.out.println("434521 -> " + result );

        System.out.println();
        System.out.print("Finally, some easy ones.");

        String nombre = "ERROR";
        nombre = get_name();
        System.out.println("Hi, " + nombre );

        System.out.println();
        System.out.println("Do you feel lucky, punk?");
        crash();
        System.out.println();
    }

    public static int superrand( int a, int b )
    // Parameters are:
    //	int a;
    //	int b;
    {
        // picks a number between a and b, no matter which is larger
        int c;

        if ( a < b )	// b is larger
            c = a + (int)(Math.random()*(b-a+1));
        else if ( a > b )	// a is larger
            c = b + (int)(Math.random()*(a-b+1));
        else
            c = a;	// or c = b; doesn't matter since they're equal

        return c;
    }

    public static void stepcount( int first, int last, int step )
    // Parameters are:
    //     int first;
    //     int last;
    //     int step;
    {
        // counts from 'first' to 'last' by 'step'
        // handles forward and backward
        int x;

        if ( first < last )
        {
            x = first;
            while ( x <= last )
            {
                System.out.print(x + " ");
                x = x + step;
            }
        }
        else
        {
            x = first;
            while ( x >= last )
            {
                System.out.print(x + " ");
                x = x - step;
            }
        }
    }

    public static int project_grade( int p1, int p2, int p3, int p4, int p5, int p6 )
    // Parameters are:
    //     int p1, p2, p3, p4, p5, p6;
    {
        // given six integers representing scores out of five in each of the
        // six categories for the first six weeks project: tells you your
        // overall project grade out of 100

        int overall_grade;

        overall_grade = p1 * 6;    // six points per point for the first category
        overall_grade = overall_grade + ( p2 * 6 );   // six points per point
        overall_grade = overall_grade + ( p3 * 4 );   // four points per point
        overall_grade = overall_grade + ( p4 * 2 );   // two points per point
        overall_grade = overall_grade + ( p5 * 1 );   // one point per point
        overall_grade = overall_grade + ( p6 * 1 );   // one point per point

        return overall_grade;
    }

    public static String get_name()
    // No parameters.
    {
        // finds out the user's name
        Scanner keyboard = new Scanner(System.in);

        String name;
        System.out.print("Please enter your name: ");
        name = keyboard.next();

        return name;
    }

    public static void crash()
    // No parameters.
    {
        // displays "you win" or "you lose".  You lose 90% of the time.
        String magic_word;

        if ( (int)(Math.random()*10) == 0 )
        {
            // What do you know?  We won!
            magic_word = "win";
        }
        else
        {
            // No big suprise; we lost.
            magic_word = "lose";
        }

        System.out.print("you " + magic_word);
    }
    ```
  </Tab>
</Tabs>

## 108. Keychains for Sale - [Link](https://programmingbydoing.com/a/keychains1.html)

<Tabs>
  <Tab title="Task">
    Write a program that pulls up a menu with 4 options. It should look something like...

    **Sample Output**

    ```bash theme={null}
    Ye Olde Keychain Shoppe

    1. Add Keychains to Order
    2. Remove Keychains from Order
    3. View Current Order
    4. Checkout

    Please enter your choice: 1

    ADD KEYCHAINS

    1. Add Keychains to Order
    2. Remove Keychains from Order
    3. View Current Order
    4. Checkout

    Please enter your choice: 3

    VIEW ORDER

    1. Add Keychains to Order
    2. Remove Keychains from Order
    3. View Current Order
    4. Checkout

    Please enter your choice: 4

    CHECKOUT
    ```

    * You will need to create functions for each of the 4 menu options. Entering the number will call the correct function.
    * This assignment does not require you to complete ANY of the functionality except for the working menu system. There is no need for you to program the ability to add keychains, remove keychains, view orders or checkout.
    * The functions should be named add\_keychains(), remove\_keychains(), view\_order() and checkout().
    * Each function should print a message that it has been called.
    * The user should be able to keep putting in choices until the checkout() function is called. When checkout() is finished, the program should end.
  </Tab>

  <Tab title="Code">
    ```java Keychains1.java theme={null}
    import java.util.Scanner;

    public class Keychains1
    {
        public static void main( String[] args )
        {
            Scanner keyboard = new Scanner(System.in);
            int choice;

            System.out.println("Ye Olde Keychain Shoppe\n");

            do
            {
                System.out.println("1. Add Keychains to Order");
                System.out.println("2. Remove Keychains from Order");
                System.out.println("3. View Current Order");
                System.out.println("4. Checkout\n");
                System.out.print("Please enter your choice: ");
                choice = keyboard.nextInt();

                if ( choice == 1 )
                {
                    add_keychains();
                }
                else if ( choice == 2 )
                {
                    remove_keychains();
                }
                else if ( choice == 3 )
                {
                    view_order();
                }
                else if ( choice == 4 )
                {
                    checkout();
                }
                else
                {
                    System.out.println("Invalid choice.");
                }
            } while ( choice != 4 );
        }

        public static void add_keychains()
        {
            System.out.println("\nADD KEYCHAINS\n");
        }

        public static void remove_keychains()
        {
            System.out.println("\nREMOVE KEYCHAINS\n");
        }

        public static void view_order()
        {
            System.out.println("\nVIEW ORDER\n");
        }

        public static void checkout()
        {
            System.out.println("\nCHECKOUT\n");
        }
    }
    ```
  </Tab>
</Tabs>

## 109. Keychains for Sale, for real this time - [Link](https://programmingbydoing.com/a/keychains2.html)

<Tabs>
  <Tab title="Task">
    Okay, now it is time to make the [keychain shop](https://programmingbydoing.com/a/keychains1.html) actually work.

    **Sample Output**

    ```bash theme={null}
    Ye Olde Keychain Shoppe

    1. Add Keychains to Order
    2. Remove Keychains from Order
    3. View Current Order
    4. Checkout

    Please enter your choice: 1

    You have 0 keychains. How many to add? 3
    You now have 3 keychains.

    1. Add Keychains to Order
    2. Remove Keychains from Order
    3. View Current Order
    4. Checkout

    Please enter your choice: 2

    You have 3 keychains. How many to remove? 1
    You now have 2 keychains.

    1. Add Keychains to Order
    2. Remove Keychains from Order
    3. View Current Order
    4. Checkout

    Please enter your choice: 3

    You have 2 keychains.
    Keychains cost $10 each.
    Total cost is $20.

    1. Add Keychains to Order
    2. Remove Keychains from Order
    3. View Current Order
    4. Checkout

    Please enter your choice: 4

    CHECKOUT

    What is your name? Biff
    You have 2 keychains.
    Keychains cost $10 each.
    Total cost is $20.
    Thanks for your order, Biff!
    ```

    * You will need 2 new variables in main, one to store the current number of keychains, and one to store the price per keychain.
    * The price should be \$10 per keychain.
    * add\_keychains() will need to be passed one int, and have a return type of int. It will ask the user for the number of keychains to add to the order, and then return the new number of keychains.
    * remove\_keychains() will need to be passed one int, and have a return type of int. It will ask the user for the number of keychains to remove from the order, and then return the new number of keychains.
    * view\_order() will need to be passed two ints, and have a return type of void. It will display, on three different lines, the number of keychains in the order, the price per keychain, and the total cost of the order.
    * checkout() will need to be passed two ints, and have a return type of void. It will ask the user for his/her name in order to deliver them correctly, display the order information, and then thank the user, by name, for ordering.
  </Tab>

  <Tab title="Code">
    ```java Keychains2.java theme={null}
    import java.util.Scanner;

    public class Keychains2
    {
        public static void main( String[] args )
        {
            Scanner keyboard = new Scanner(System.in);
            int choice;
            int keychains = 0;
            int price = 10;

            System.out.println("Ye Olde Keychain Shoppe\n");

            do
            {
                System.out.println("1. Add Keychains to Order");
                System.out.println("2. Remove Keychains from Order");
                System.out.println("3. View Current Order");
                System.out.println("4. Checkout\n");
                System.out.print("Please enter your choice: ");
                choice = keyboard.nextInt();

                if ( choice == 1 )
                {
                    keychains = add_keychains(keychains);
                }
                else if ( choice == 2 )
                {
                    keychains = remove_keychains(keychains);
                }
                else if ( choice == 3 )
                {
                    view_order(keychains, price);
                }
                else if ( choice == 4 )
                {
                    checkout(keychains, price);
                }
                else
                {
                    System.out.println("Invalid choice.");
                }
            } while ( choice != 4 );
        }

        public static int add_keychains( int keychains )
        {
            Scanner keyboard = new Scanner(System.in);
            int add;

            System.out.printf("\nYou have %s keychains. How many to add? ", keychains);
            add = keyboard.nextInt();
            keychains += add;
            System.out.printf("You now have %s keychains.\n\n", keychains);

            return keychains;
        }

        public static int remove_keychains( int keychains )
        {
            Scanner keyboard = new Scanner(System.in);
            int remove;

            System.out.printf("\nYou have %s keychains. How many to remove? ", keychains);
            remove = keyboard.nextInt();
            keychains -= remove;
            System.out.printf("You now have %s keychains.\n\n", keychains);

            return keychains;
        }

        public static void view_order( int keychains, int price )
        {
            System.out.printf("\nYou have %s keychains.\n", keychains);
            System.out.printf("Keychains cost $%s each.\n", price);
            System.out.printf("Total cost is $%s.\n\n", keychains * price);
        }

        public static void checkout( int keychains, int price )
        {
            Scanner keyboard = new Scanner(System.in);
            String name;
            System.out.print("\nCHECKOUT\n\n");

            System.out.print("What is your name? ");
            name = keyboard.next();
            System.out.printf("You have %s keychains.\n", keychains);
            System.out.printf("Keychains cost $%s each.\n", price);
            System.out.printf("Total cost is $%s.\n", keychains * price);
            System.out.printf("Thanks for your order, %s!\n", name);
        }
    }
    ```
  </Tab>
</Tabs>