Methods

Parameters, return types, overloading and how arguments are passed.

A method has a return type, a name and parameters. Use void when it returns nothing.

Java

public class Main {
  static int add(int a, int b) {
    return a + b;
  }

  static double add(double a, double b) {
    return a + b;
  }

  public static void main(String[] args) {
    System.out.println(add(2, 3));
    System.out.println(add(2.5, 3));
  }
}

Output

5
5.5

Two methods with one name but different parameter types is called overloading. Java picks the match at compile time.

Java passes by value

A method gets a copy of the value. For an object, that value is a reference, so the method can change the object itself but cannot make your variable point somewhere else.

Java

public class Main {
  static void change(int n, int[] arr) {
    n = 99;
    arr[0] = 99;
  }

  public static void main(String[] args) {
    int n = 1;
    int[] arr = {1};
    change(n, arr);
    System.out.println(n + " " + arr[0]);
  }
}

Output

1 99

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