Parameters and Arguments

Example

public class Main {
    static void greet(String name, int age) {
        System.out.println("Hi " + name + ", you are " + age);
    }

    static void printReceipt(String item, int qty, double price) {
        System.out.printf("%s x%d = Rs. %.2f%n", item, qty, qty * price);
    }

    public static void main(String[] args) {
        greet("Rahul", 23);
        greet("Divya", 21);
        printReceipt("Notebook", 3, 45.0);
        printReceipt("Pen", 10, 12.5);
    }
}

Output

Hi Rahul, you are 23
Hi Divya, you are 21
Notebook x3 = Rs. 135.00
Pen x10 = Rs. 125.00

Example

Java always passes a copy of the argument. Changing a primitive parameter does not affect the caller. For arrays and objects the copy is a copy of the reference, so the method can change the object it points to.

import java.util.Arrays;

public class Main {
    static void tryToChange(int x) {
        x = 100;
    }

    static void addBonus(int[] marks) {
        for (int i = 0; i < marks.length; i++) marks[i] += 5;
    }

    public static void main(String[] args) {
        int value = 10;
        tryToChange(value);
        System.out.println("value = " + value);

        int[] marks = {60, 70};
        addBonus(marks);
        System.out.println("marks = " + Arrays.toString(marks));
    }
}

Output

value = 10
marks = [65, 75]

Example

A parameter written as type... name accepts any number of arguments (it becomes an array).

public class Main {
    static int sum(int... numbers) {
        int total = 0;
        for (int n : numbers) total += n;
        return total;
    }

    public static void main(String[] args) {
        System.out.println(sum());
        System.out.println(sum(5));
        System.out.println(sum(1, 2, 3, 4));
    }
}

Output

0
5
10