Question

I have 2 questions:

1. In Java how are the arguments passed in methods? By reference or by copy?
2. Can you give some code examples? thanks

Answer 1

As you stated in your question: there are 2 types of passing an argument in methods in various different programming languages:

• Passing to a method by COPY: The method recieves a copy of the variable
• Passing to a method by REFERENCE: The method recieves a reference to the origianl object

In Java the arguments ARE ALWAYS PASSED BY COPY!

Here is some code with given examples:

public class ArgumentsPass {

    public static void main(String[] args) {

        int original = 10;
        System.out.println("Original int before: " + original);
        incrementValue(original);
        System.out.println("Original int after: " + original);

        System.out.println("**********************************");

        String original2 = "Original!";
        System.out.println("Original String before: " + original2);
        changeString(original2);
        System.out.println("Original String after: " + original2);
    }

    static void incrementValue(int inMethod) {//METHOD 1: incrementValue
        inMethod++;
        System.out.println("In method int is: " + inMethod);
    }

    static void changeString(String inMethod) {//METHOD 2: changeString
        inMethod = "New!";
        System.out.println("In method String is: " + inMethod);
    }
}

The output is:

Original int before: 10
In method int is: 11
Original int after: 10
**********************************
Original String before: Original!
In method String is: New!
Original String after: Original!