An immutable class in Java is one whose instances cannot be modified once created. In other words, It’s like an object with a fixed state that cannot be modified.
In this article, we will explore the captivating realm of immutable classes in Java, exploring their significance, the rules for crafting them, and real-world applications.
What is Immutability?
Before we start our discussion about the immutable class, let’s start with the basics. Immutability in Java refers to the property of an object or class whose instances cannot be altered after creation.
Why We Need Immutable Classes in Java?
Why bother with immutable classes? you might ask. Well, there are somany reasons why we need immutable classes in Java programming. But let us point out some of the key reasons below:
Thread Safety: In Java, multi-threading is a common practice. Immutability ensures that objects can be safely shared among multiple threads without the risk of data corruption or race conditions. Since immutable objects cannot change, concurrent access is inherently safe.
Predictable Behavior: Immutability guarantees that the state of an object remains constant after creation. This predictability simplifies debugging and makes code easier to reason about because you don’t have to consider unexpected changes to the object state.
Caching: Immutable objects can be safely cached. Once created, they can be reused without worrying about modifications. This can lead to performance improvements by reducing the need to recreate objects repeatedly.
Simplified Code: Immutability encourages a functional programming style, where functions/methods return new objects with modified state instead of modifying the original object. This leads to cleaner, more maintainable code.
Value Semantics: Immutable objects represent values rather than entities with identity. This aligns well with Java’s equals and hashCode contract, making it easier to compare and use immutable objects in collections like HashMap or HashSet.
Defensive Copy Avoidance: In some cases, immutability can eliminate the need for defensive copying of objects, which can be a performance bottleneck in certain scenarios.
Security: Immutable objects are less prone to security vulnerabilities. Since their state cannot change, they are less susceptible to unauthorized modifications by malicious code.
Functional Programming: Immutability is a fundamental concept in functional programming. Learning to work with immutable objects in Java can help developers transition to functional programming paradigms and take advantage of features introduced in modern Java versions.
Best Practice to Create Immutable Classes in Java
After clarifying your doubt about why we need an immutable class in Java, you may be thinking about how we can create an immutable class in Java. So before discussing how to create, we need to spare some time to understand the best practices or guidelines we need to follow.
Make the Class Final: To prevent inheritance and subclassing, declare the class final. This ensures that no one can create a mutable subclass that modifies the class’s behavior.
public final class ImmutableClass
{
// Code Here.....
}
Declare Fields as Private and Final: The class’s instance variables (fields) should be declared as private and marked as final. This ensures that the fields cannot be modified after object creation.
public final class ImmutableClass
{
private final int id;
private final String name;
public ImmutableClass(int id, String name)
{
this.id = id;
this.name = name;
}
// ...
}
Provide Only Getter Methods: Create getter methods to access the fields but do not provide any setter methods. This enforces read-only access to the class’s attributes.
public final class ImmutableClass
{
private final int id;
private final String name;
public ImmutableClass(int id, String name)
{
this.id = id;
this.name = name;
}
public int getId()
{
return id;
}
public String getName()
{
return name;
}
}
Do Not Modify Fields Internally: Ensure that no methods within the class modify the state of the fields. If you need to create a modified version of the object, return a new object with the desired changes.
public final class ImmutableClass
{
private final int id;
private final String name;
public ImmutableClass(int id, String name)
{
this.id = id;
this.name = name;
}
public int getId() {
return id;
}
public String getName()
{
return name;
}
public ImmutableClass withName(String newName)
{
return new ImmutableClass(this.id, newName);
}
}
Initialize Fields in the Constructor: Initialize all fields in the constructor. Once set, they cannot be modified.
Immutable Class In Java Example
Now, Let’s create an immutable class by following the above guidelines:
public final class ImmutableClassEx
{
final String blogName;
final String url;
// Constructor to Initilize the Variables
public ImmutableClassEx(String blogName, String url)
{
this.blogName = blogName;
this.url = url;
}
public String getBlogName()
{
return blogName;
}
public String getUrl()
{
return url;
}
public static void main(String[] args)
{
ImmutableClassEx obj=new ImmutableClassEx("SoftwareTestingo", "https://www.softwaretestingo.com");
System.out.println("The Blog Name: "+obj.getBlogName());
System.out.println("URL Of Blog: "+obj.getUrl());
}
}
Output:
The Blog Name: SoftwareTestingo URL Of Blog: https://www.softwaretestingo.com
Conclusion:
Understanding the concept of immutable classes in Java is essential for writing robust and reliable software development. Immutability provides thread safety predictability and simplifies code, making it a valuable practice in Java development.
If you have any questions about immutable Java classes, please don’t hesitate to comment below. We’re here to help clarify any uncertainties and provide further explanations.
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