Statement = a line of code that performs a basic operation
Method = a named sequence of statements
Usage:
- to do non-simple operations repeatedly
- to break complex problems into smaller, simpler parts

Types of Methods

VOID Method	VALUE Method
Does not return a value	Returns a value
Often referred to as a procedure	Often referred to as a function

Void Method

public static void sayHello() {
    System.out.println("Hello");
}

public static void sayHello(String name) {
    System.out.println("Hello " + name);
}

public static void main(String[] args) {
    sayHello();
    sayHello("Ani");
}

Penjelasan

Method Names
Parameters and Arguments
Statements
Overloading

Exercise Void Method

Exercise 1
Solution Exercise 1

Write one or several methods to do the following

Prints a String n times
Display the message “Good Morning” in various languages
Display an alphanumeric character as an ASCII art

public static void printString(String str, int n) {
    for (int i = 0; i < n; i++) {
        System.out.println(str);
    }
}

Value Method

public static double computeBMI(double weight, double height) {
    double bmi = weight / height / height;
    return bmi;
}

public static void main(String[] args) {
    double weight = 40;
    double height = 1.65;
    double bmi = computeBMI(weight, height);

    System.out.println("Ani's BMI is: " + bmi);
}

Penjelasan

Return type and value

Exercise Value Method

Exercise 1
Solution Exercise 1

Write one or several methods to do the following

Calculates the distance between two coordinates
Determines whether a number is prime or not
Determines the number of days in a year

public static double distance(double x1, double y1, double x2, double y2) {
    double dx = x2 - x1;
    double dy = y2 - y1;
    return Math.sqrt(dx * dx + dy * dy);
}

Method Composition

public static double computeTax(double price) {
    double tax = 0;
    if (price > 100) {
        tax = 0.2 * price;
    }
    return tax;
}

public static double computePayment(double price) {
    return price + computeTax(price);
}

public static void main(String[] args) {
    double itemPrice = 600;
    double payment = computePayment(itemPrice);
}

Recursive Methods

https://keenformatics.blogspot.com/2013/08/how-to-solve-json-infinite-recursion.html

A method that invokes itself
example:

    0! = 1
    n! = n ∙ (n – 1)!

    factorial(5) = 5 _ factorial(4)
    factorial(4) = 4 _ factorial(3)
    factorial(3) = 3 _ factorial(2)
    factorial(2) = 2 _ factorial(1)
    factorial(1) = 1 * factorial(0)
    factorial(0) = 1

public static int factorial(int n) {
    if (n == 0) {
        return 1;
    }
    return n * factorial(n - 1);
}

public static void main(String[] args) {
    System.out.println(factorial(5));
}

Write the base case:

if (n == 0) {
    return 1;
}

Write the reduction step. Ensure that the base case can be reached:

return n * factorial(n - 1);

Recursion vs Iteration

Recursion is not always needed
Everything that can be done with recursion can be done using iterations (loops)
Recursion
- consumes more memory and slower than iterations
- elegant, shorter code

Documentation

True
False

Persiapan Belajar

Materi

Task

Programming by Doing

Compiler

Methods

Types of Methods

Void Method

Exercise Void Method

Value Method

Exercise Value Method

Method Composition

Recursive Methods

Recursion vs Iteration

Documentation

​Types of Methods

​Void Method

​Exercise Void Method

​Value Method

​Exercise Value Method

​Method Composition

​Recursive Methods

​Recursion vs Iteration

​Documentation

Types of Methods

Void Method

Exercise Void Method

Value Method

Exercise Value Method

Method Composition

Recursive Methods

Recursion vs Iteration

Documentation