Write a program to print integers from 1 to 6Output:
1
2
3
4
5
6

    public class Main {
        public static void main(String[] args) {
            for (int i = 1; i <= 6; i++) {
                System.out.println(i);
            }
        }
    }

    public class Main {
        public static void main(String[] args) {
            int n = 7, first = 0, second = 1;
            for (int i = 1; i <= n; i++) {
                System.out.print(second + " ");
                int next = first + second;
                first = second;
                second = next;
            }
        }
    }

    public class Main {
        public static void main(String[] args) {
            int n = 12;
            for (int i = 1; i <= n; i++) {
                if (n % i == 0) {
                    System.out.print(i + " ");
                }
            }
        }
    }

`for` Loop

Example
Flowchart

  for (initialization; condition; update statement) {
      // do something
  }

  for (int i = 1; i <= 10; i++) {
      System.out.println(i);
  }
  for (int i = 0; i < 10; i++) {
      System.out.println(i + 1);
  }

int sum = 0;
for (int i = 0; i < 5; i++) {
    sum = sum + i;
}
System.out.println(sum);

Example `for` Loop

Example 1
Example 2
Example 3

int n = 5;
for (int i = 1, j = n; i <= n && j > 0; i++, j--) {
    System.out.println(i + " - " + j);
}

Output:
1 - 5
2 - 4
3 - 3
4 - 2
5 - 1

int n = 5, i = 1, j = n;
for (; i <= n && j > 0;) {
    System.out.println(i + " - " + j);
    i++;
    j--;
}

Output:
1 - 5
2 - 4
3 - 3
4 - 2
5 - 1

for (;;) {
    System.out.println("Hello");
}

Output:
Hello
Hello
Hello
Hello
...

Exercise `for` Loop

Write a program using for loop to print odd integers from 1 to n (inclusive).Sample input:
10Sample output:
1 3 5 7 9

import java.util.Scanner;
public class OddNumbers {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        for (int i = 1; i <= n; i += 2) {
            System.out.print(i + " ");
        }
    }
}

Write a program using for loop to determine whether the number entered by the user is a prime number or not.
Prime numbers are positive integers which are only divisible by 1 or the number itself. Examples: 2, 3, 5, 7, …Sample input:
5
Sample output:
PrimeSample input:
10
Sample output: Not Prime

import java.util.Scanner;
public class PrimeNumber {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        boolean isPrime = true;
        for (int i = 2; i <= n / 2; i++) {
            if (n % i == 0) {
                isPrime = false;
                break;
            }
        }
        if (isPrime) {
            System.out.println("Prime");
        } else {
            System.out.println("Not Prime");
        }
    }
}

The following code should display the character ”*” 42 times. However, the programmer who wrote it made a mistake.

    int n = 42;
    for (int i = 0; i < n; i--) {
        System.out.print("*");
    }

Fix the code using only one of the following ways:

Add one character
Delete one character
Replace one character with another character

int n = 42;
for (int i = 0; i < n; i++) {
    System.out.print("*");
}

`while` Loop

Example
Flowchart

  while (condition) {
      // do something
  }

  int n = 1;
  while (n <= 5) {
      System.out.println(n);
      n++;
  }

int i = 5, sum = 0;
while (i > 0) {
    sum = sum + i;
    i--;
}
System.out.println(sum);

Exercise `while` Loop

Exercise 1
Solution Exercise 1
Exercise 2
Solution Exercise 2

Write a program using while loop to print integers from n to 1.Sample input: 10Sample output: 10 9 8 7 6 5 4 3 2 1

import java.util.Scanner;
public class PrintNumbers {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        while (n > 0) {
            System.out.print(n + " ");
            n--;
        }
    }
}

import java.util.Scanner;
public class Average {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int sum = 0, count = 0;
        while (true) {
            int n = sc.nextInt();
            if (n == -1) {
                break;
            }
            sum += n;
            count++;
        }
        System.out.println((double) sum / count);
    }
}

`do-while` Loop

Example
Flowchart

  do {
      // do something
  } while (condition);

  int n = 10;
  do {
      System.out.println(n);
      n--;
  } while (n > 0);

int i = 5, sum = 0;
do {
    sum = sum + i;
    i--;
} while (i > 0);
System.out.println(sum);

Example `do-while` Loop

double number;
do {
    System.out.print("Enter a positive number: ");
    number = input.nextDouble();
} while (number <= 0);
System.out.println("You entered " + number);

Exercise `do-while` Loop

Exercise 1
Solution Exercise 1

Write a program using do-while loop to display the multiplication table of numbers entered by the user.Sample input:
5Sample output:
5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
5 x 6 = 30
5 x 7 = 35
5 x 8 = 40
5 x 9 = 45
5 x 10 = 50\

import java.util.Scanner;
public class MultiplicationTable {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int i = 1;
        do {
            System.out.println(n + " x " + i + " = " + n * i);
            i++;
        } while (i <= 10);
    }
}

`Nested` Loops

Sample 1
Sample 2
Sample 3

for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 10; j++) {
        // do something
    }
}

boolean ok = false;

while (!ok) {
    for (int i = 0; i < 10; i++) {
        // do something
        if (condition) {
            ok = true;
        }
        // ....
    }
}

for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 10; j++) {
        System.out.println(i + "-" + j);
    }
}

Exercise `Nested` Loops

Exercise 1 Rectangle

Question
Solution

Make a program to display m × n rectangles formed with star characters (*). m is the length of the rectangle, and n is its width.Sample Input:
7 3Sample Output:
* * * * * * *
* * * * * * *
* * * * * * *

import java.util.Scanner;
public class Rectangle {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int m = sc.nextInt();
        int n = sc.nextInt();
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                System.out.print("* ");
            }
            System.out.println();
        }
    }
}

Exercise 2 NumericTriangle

Question
Solution

Write a program to display a numeric triangle illustrated as follows.Sample Input:
5Sample Output:
1
12
123
1234
12345

import java.util.Scanner;
public class NumericTriangle {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= i; j++) {
                System.out.print(j);
            }
            System.out.println();
        }
    }
}

Exercise 3 NumericTriangle2

Question
Solution

Write a program to display a numeric triangle illustrated as follows.Sample Input:
5Sample Output:

~~~~~~~

~~~~~

~~~

123

~

1234
12345

import java.util.Scanner;
public class NumericTriangle {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n - i; j++) {
                System.out.print(" ");
            }
            for (int j = 1; j <= i; j++) {
                System.out.print(j);
            }
            System.out.println();
        }
    }
}

Exercise 4 NumericTriangle3

Question
Solution

Write a program to display a numeric triangle illustrated as follows.Sample Input:
5Sample Output:

~~~~~~~

~~~~~

121

~~~

12321

~

1234321
123454321

import java.util.Scanner;
public class NumericTriangle {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n - i; j++) {
                System.out.print(" ");
            }
            for (int j = 1; j <= i; j++) {
                System.out.print(j);
            }
            for (int j = i - 1; j >= 1; j--) {
                System.out.print(j);
            }
            System.out.println();
        }
    }
}

Exercise 5 NumericTriangle4

Question
Solution

Write a program to display a numeric triangle illustrated as follows.Sample Input:
n = 5Sample Output:

~~~~~~~

~~~~~

121

~~~

12321

~

1234321
123454321

~

1234321

~~~

12321

~~~~~

121

~~~~~~~

import java.util.Scanner;
public class NumericTriangle {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("n: ");
        int n = sc.nextInt();

        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n - i; j++) {
                System.out.print(" ");
            }

            for (int j = 1; j <= i; j++) {
                System.out.printf("%s", j % 10);
            }

            for (int j = i - 1; j >= 1; j--) {
                System.out.printf("%s", j % 10);
            }
            System.out.println();
        }

        for (int i = n - 1; i >= 1; i--) {
            for (int j = 1; j <= n - i; j++) {
                System.out.print(" ");
            }

            for (int j = 1; j <= i; j++) {
                System.out.printf("%s", j % 10);
            }

            for (int j = i - 1; j >= 1; j--) {
                System.out.printf("%s", j % 10);
            }
            System.out.println();
        }
    }
}

`break` dan `continue`

for (int i = 0; i < 10; i++) {
    if (i == 2) {
        continue; #To the next iteration
    } else if (i == 7) {
        break;    #Exit Loop
    }
    System.out.println(i);
}

Using `break`

Scanner in = new Scanner(System.in);
boolean ok = false;
while (!ok) {
    System.out.print("Enter a number: ");
    if (in.hasNextDouble()) {
        ok = true;
    } else {
        String word = in.next();
        System.out.println(word + " is not a number");
    }
}
double x = in.nextDouble();

Scanner in = new Scanner(System.in);
while (true) {
    System.out.print("Enter a number: ");
    if (in.hasNextDouble()) {
        break;
    }
    String word = in.next();
    System.out.println(word + " is not a number");
}
double x = in.nextDouble();

Using `continue`

Scanner in = new Scanner(System.in);
int x = -1;
int sum = 0;
while (x != 0) {
    x = in.nextInt();
    if (x <= 0) {
        continue;
    }
    System.out.println("Adding " + x);
    sum += x;
}
System.out.println(sum);

Exercise `break` dan `continue`

Exercise 1
Solution Exercise 1
Exercise 2
Solution Exercise 2

By using break or continue, write a program to determine whether the number entered by the user is a prime number or not.Sample Input:
5Sample Output:
Prime

import java.util.Scanner;
public class PrimeNumber {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        boolean isPrime = true;
        for (int i = 2; i <= n / 2; i++) {
            if (n % i == 0) {
                isPrime = false;
                break;
            }
        }
        if (isPrime) {
            System.out.println("Prime");
        } else {
            System.out.println("Not Prime");
        }
    }
}

import java.util.Scanner;
public class GCD {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int gcd = 1;
        for (int i = 1; i <= a && i <= b; i++) {
            if (a % i == 0 && b % i == 0) {
                gcd = i;
            }
        }
        System.out.println(gcd);
    }
}

Tambahan Materi `Nested` Loops di kelas

Exercise 1 Digit Sum Sequence

Question
Solution

Tulis sebuah code program untuk menghitung total dari angka yang diinputkan oleh user.Sample Input:
Masukkan angka: = 12345Sample Output:
5 4 3 2 1
sum of digits: = 15

DigitSumSequence.java

import java.util.Scanner;
public class DigitSumSequence {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.print("Masukkan angka: ");
        int number = input.nextInt();

        int sum = 0;
        do {
            int lastDigit = number % 10;
            System.out.printf("%d ", lastDigit);
            sum += lastDigit;
            number /= 10;
        } while (number > 0);

        System.out.println("\nsum of digits: " + sum);
    }
}

Exercise 2 Nested Digit Sum Sequence one digit

Question
Solution

Tulis sebuah code program untuk menghitung total dari angka yang diinputkan oleh user.Sample Input:
Masukkan angka: = 12345Sample Output:
5 4 3 2 1
sum of digits: = 15
5 1
sum of digits: = 6\

NestedDigitSumSequence.java

import java.util.Scanner;
public class NestedDigitSumSequence {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.print("Masukkan angka: ");
        int number = input.nextInt();

        int sum = 0;
        do {
            int temp = number;
            sum = 0;
            while (temp > 0) {
                int lastDigit = temp % 10;
                System.out.printf("%d ", lastDigit);
                sum += lastDigit;
                temp /= 10;
            }
            System.out.println();
            System.out.println("sum of digits: " + sum);
            number = sum;
        } while (sum > 9);
    }
}

Exercise 3 Fibonacci Custom Sum

Question
Solution

Sample Output:
1 1 2 3 5 8 13 12 7 10 8 9 17 17 16 15 13 10 5 6 11 …

FibonacciCustomSum.java

public class FibonacciCustomSum {
    public static void main(String[] args) {
        int a = 1;
        int b = 1;

        System.out.print(a + " " + b + " ");

        for (int i = 3; i <= 1000; i++) {
            int sum = digitSum(a) + digitSum(b);
            System.out.print(sum + " ");
            a = b;
            b = sum;
        }
    }

    public static int digitSum(int digit) {
        int number = digit;
        int sum = 0;
        while (number > 0) {
            int lastDigit = number % 10;
            sum += lastDigit;
            number /= 10;
        }
        return sum;
    }
}

Exercise 4 Check Digit Sum

Question
Solution

Status Exercise ProgressSample Input:
Masukkan angka: = 123
Masukkan angka: = 456
Masukkan angka: = 451Sample Output:
1 + 2 = 3 (memenuhi syarat)
4 + 5 = 6 (tidak memenuhi syarat)
4 + 1 = 5 (memenuhi syarat)

CheckDigitSum.java

import java.util.Scanner;
public class CheckDigitSum {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.print("Masukkan angka: ");
        int n = input.nextInt();

        int number = n;
        int max = 0;
        int sum = 0;
        while (number > 0) {
            int lastDigit = number % 10;
            sum += lastDigit;
            max = Math.max(max, lastDigit);
            number /= 10;
        }

        if (sum == max * 2) {
            System.out.printf("%d digits (memenuhi syarat)%n", n);
        } else {
            System.out.printf("%d digits (tidak memenuhi syarat)%n", n);
        }
    }
}

Persiapan Belajar

Materi

Task

Programming by Doing

Compiler

Loops

`for` Loop

Example `for` Loop

Exercise `for` Loop

`while` Loop

Exercise `while` Loop

`do-while` Loop

Example `do-while` Loop

Exercise `do-while` Loop

`Nested` Loops

Exercise `Nested` Loops

`break` dan `continue`

Using `break`

Using `continue`

Exercise `break` dan `continue`

Tambahan Materi `Nested` Loops di kelas

​for Loop

​Example for Loop

​Exercise for Loop

​while Loop

​Exercise while Loop

​do-while Loop

​Example do-while Loop

​Exercise do-while Loop

​Nested Loops

​Exercise Nested Loops

​break dan continue

​Using break

​Using continue

​Exercise break dan continue

​Tambahan Materi Nested Loops di kelas

`for` Loop

Example `for` Loop

Exercise `for` Loop

`while` Loop

Exercise `while` Loop

`do-while` Loop

Example `do-while` Loop

Exercise `do-while` Loop

`Nested` Loops

Exercise `Nested` Loops

`break` dan `continue`

Using `break`

Using `continue`

Exercise `break` dan `continue`

Tambahan Materi `Nested` Loops di kelas