Method Arguments and Call by Value in Java
Table of Contents:
- Introduction
- Method Arguments in Java
- Call by Value in Java
- Example Code: Call by Value
- Key Takeaways
- Conclusion
Introduction
In this eBook, we will explore the concept of method arguments and the mechanism known as “Call by Value” in Java. These are fundamental concepts that every Java developer should be familiar with, as they play a crucial role in how data is passed to methods in Java applications.
We will cover what method arguments are, explain the differences between call by value and call by reference, and provide a practical example to illustrate how Java implements this concept. By the end of this eBook, you’ll understand why Java uses call by value and how it affects the behavior of your methods.
Method Arguments in Java
What Are Method Arguments?
In Java, method arguments are values or variables passed to a method when it is called. These arguments are used by the method to perform specific operations. For example, in mathematical functions, the inputs (arguments) could be numbers, and the output could be the result of an operation on these numbers.
Here is a simple method with an argument:
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void displayValue(int value) { System.out.println("Value: " + value); } |
When calling this method, you provide an integer value, which the method prints.
Call by Value in Java
Explanation
Java employs a mechanism known as call by value when passing arguments to methods. This means that when an argument is passed to a method, a copy of the actual value is created. The method works with this copy, so any changes made to the argument inside the method do not affect the original value.
This is important because it differs from the concept of call by reference, where changes to the argument inside the method would affect the original variable outside the method. In Java, since only the value is passed, the original variable remains unchanged.
Example Code
Below is an example of a Java program demonstrating call by value:
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package org.studyeasy; public class Main { public static void main(String[] args) { int value = 10; Main main = new Main(); System.out.println("main method : " + value); main.displayValue(value); System.out.println("main method : " + value); } void displayValue(int value) { System.out.println("Display method : " + value); value = 20; System.out.println("Display method : " + value); } } |
Explanation of the Code
1. Main Method:
In the main method, we initialize the variable value with 10 and then print it.
We then call the displayValue() method, passing value as an argument.
2. displayValue() Method:
Inside this method, the value of the value variable is printed.
Then, we change the value to 20 and print it again.
When you run this program, you’ll see that the changes made to value inside the displayValue() method do not affect the original value in the main() method.
Output
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main method : 10 Display method : 10 Display method : 20 main method : 10 |
Key Takeaways
- Method Arguments: The inputs provided to a method in Java.
- Call by Value: A mechanism in which a copy of the argument is passed to the method, and changes made to the argument inside the method do not affect the original value.
- Java does not support call by reference, and objects are also passed by value, though this can sometimes be misunderstood as reference behavior due to object mutability.
Conclusion
Understanding how Java handles method arguments through call by value is crucial for writing efficient and predictable code. By knowing that Java creates copies of variables when passing them to methods, developers can better manage their programs’ behavior, especially when working with complex data structures.