Java Call by Value

In Java, arguments are passed to methods using a mechanism called "call by value." This guide will explore the concept of call by value, its syntax, and how it works in Java.

Syntax

In Java, when a method is called, values of the arguments are passed to the parameters of the method:

public void myMethod(int parameter1, String parameter2) {
    // Method body
}

Example

Let's consider an example to illustrate call by value:

public class CallByValueExample {

    public static void main(String[] args) {
        int number = 10;

        System.out.println("Before calling modifyValue method: " + number);
        modifyValue(number);
        System.out.println("After calling modifyValue method: " + number);
    }

    public static void modifyValue(int value) {
        System.out.println("Inside modifyValue method (before modification): " + value);
        value = 20;
        System.out.println("Inside modifyValue method (after modification): " + value);
    }
}

Output

The output will demonstrate that the original value outside the method remains unchanged:

Before calling modifyValue method: 10
Inside modifyValue method (before modification): 10
Inside modifyValue method (after modification): 20
After calling modifyValue method: 10

Explanation

• The modifyValue method takes an argument value, which is a copy of the original value passed to it.
• Modifying the value inside the method does not affect the original value outside the method.

Use

Understanding call by value is important:

• When working with primitive data types (int, float, char, etc.).
• When passing the value of an object reference, which is actually a memory address.

Important Points

• In call by value, a copy of the actual value is passed to the method parameter.
• Changes made to the parameter inside the method do not affect the original value outside the method.
• For objects, the value passed is a copy of the reference, not the actual object.

Summary

Java uses call by value to pass arguments to methods, meaning a copy of the actual value is passed. Changes made to the parameters inside the method do not impact the original values outside the method. Understanding this mechanism is fundamental for writing reliable and predictable Java code.