What is the significance of the final keyword when applied to classes, methods, and variables?

Question

Ravi Vishwakarma · Answer

The final keyword in Java can be applied to classes, methods, and variables, and it serves different purposes in each context. Here is an explanation of its significance:
1. Final Classes
When a class is declared as final, it cannot be subclassed. This means no other class can extend a
final class.
Significance:
Security: Prevents inheritance, which can be useful when creating immutable classes or ensuring the integrity of a class's behavior.Performance: The JVM can optimize calls to final classes more effectively because it knows that the class will not be extended.
Example:
public final class ImmutableClass {
    private final int value;
    public ImmutableClass(int value) {
        this.value = value;
    }
    public int getValue() {
        return value;
    }
}
// This will cause a compile-time error
// public class SubClass extends ImmutableClass {}
2. Final Methods
When a method is declared as final, it cannot be overridden by subclasses.
Significance:
Consistency: Ensures that the method's behavior remains unchanged across all subclasses.Security: Prevents subclasses from altering crucial methods, maintaining the integrity of the class's behavior.Performance: The JVM can optimize calls to final methods more effectively.
Example:
public class ParentClass {
    public final void show() {
        System.out.println("This is a final method.");
    }
}
public class ChildClass extends ParentClass {
    // This will cause a compile-time error
    // public void show() {}
}
3. Final Variables
When a variable is declared as final, its value cannot be changed once it is initialized, this applies to instance, static, and local variables.
Significance:
Constants: Useful for defining constants. A final variable acts as a constant whose value is set once and cannot be modified.Immutability: Helps create immutable objects by ensuring that the state cannot be changed after construction.Thread Safety: Reduces data corruption risks in concurrent applications by ensuring that the value remains constant after initialization.
Example:
public class Constants {
    public static final double PI = 3.14159;
    public static void main(String[] args) {
        final int fixedValue = 10;
        // This will cause a compile-time error
        // fixedValue = 20;
    }
}
the final keyword appropriately, developers can create more secure, reliable, and optimized Java applications.
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What is the significance of the final keyword when applied to classes, methods, and variables?

Anubhav Kumar

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1 Answers

1. Final Classes

2. Final Methods

3. Final Variables

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