Method Arguments and Call by Reference in Java
Table of Contents
- Introduction to Method Arguments and Call by Reference in Java
- Understanding Call by Reference in Java
- Example Code Walkthrough
- Advantages and Use Cases of Call by Reference
- Conclusion
Chapter 1: Introduction to Method Arguments and Call by Reference in Java
In Java, method arguments play a critical role in passing data between different parts of a program. Two common approaches to passing arguments are call by value and call by reference. Java uses call by value when passing primitive types and call by reference when passing objects or arrays. In this article, we will focus on how call by reference works in Java, how it affects arrays, and how to use it in real-world scenarios.
Chapter 2: Understanding Call by Reference in Java
In Java, when we pass an object or an array as an argument to a method, the reference to the memory location of that object or array is passed, not the actual value. This is known as call by reference. Any changes made to the object inside the method will reflect outside the method as well since both the method and the caller share the same memory location for the object.
Key Concept:
- Call by Value (Primitives): When a primitive type (e.g., int, float) is passed to a method, Java creates a copy of the variable and sends it to the method. Changes made to this copy do not affect the original variable.
- Call by Reference (Objects/Arrays): When an object or array is passed to a method, the memory reference is passed. Therefore, changes made inside the method affect the original object.
Chapter 3: Example Code Walkthrough
Now, let’s look at an example that demonstrates the concept of call by reference in Java, using arrays as the argument.
Java Code from the Project:
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package org.studyeasy; public class Main { public static void main(String[] args) { String[] names = {"Tom", "Chaand", "Study", "Easy", "Raj"}; System.out.println(names[0]); Main main = new Main(); main.displayNames(names); System.out.println("New value : " + names[0]); } void displayNames(String[] names){ System.out.println(names[0]); names[0] = "John"; } } |
Explanation:
- Array Declaration: The array
namesis initialized with five values: “Tom”, “Chaand”, “Study”, “Easy”, and “Raj”. - Passing the Array: The array is passed to the
displayNamesmethod by reference. This means thenamesarray in themainmethod and thenamesarray indisplayNamesrefer to the same memory location. - Changing the Value: Inside the
displayNamesmethod, the value at index 0 of the array is changed from “Tom” to “John”. - Effect on Original Array: After the method execution, when we print
names[0]again, it prints “John”, demonstrating that the change made inside the method affected the original array.
Output:
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Tom Tom New value : John |
Chapter 4: Advantages and Use Cases of Call by Reference
Advantages:
- Efficiency: When large objects or arrays are passed, using call by reference ensures that the program doesn’t need to create a copy of the entire object, saving both memory and processing time.
- Mutability: Objects and arrays passed by reference can be changed within methods, allowing for flexible code design, especially in scenarios involving data manipulation.
When to Use:
Call by reference is particularly useful when working with collections of data, such as arrays or object lists, where changes made in one method should be reflected globally across the program. It is also effective in situations where memory efficiency is important, such as working with large datasets or objects.
Comparison of Call by Value and Call by Reference:
| Argument Type | Behavior | Example |
|---|---|---|
| Call by Value | A copy of the value is passed. | int num = 5; Changes in method don’t affect the original variable. |
| Call by Reference | A reference to the object is passed. | String[] arr; Changes in the method affect the original object. |
Chapter 5: Conclusion
Call by reference is an important concept in Java that affects how arrays and objects behave when passed as arguments to methods. We explored how changes made inside a method reflect on the original object when using call by reference. Understanding this behavior is crucial when designing programs that manipulate collections or work with large objects.