Final Keyword In Java

The final keyword can be used with class, method, variables & parameters.

Final Class

When a final keyword is used in class declaration means a class can not be subclassed. So all methods are indirectly marked as final and can not be overridden.

Note - We can not mark class both abstract and final because abstract class must be subclassed and final class can not be subclassed.

Example

	
package com.demo;

public final class Final {

}

package com.demo;

public class TestFinal extends Final{

}

The above declaration will give this error [The type TestFinal cannot subclass the final class Final]

Final Method

When a final keyword is used with the method means that method can not be overridden in the subclass.

Note- We can not declare the method both abstract and final.

Example

package com.demo;

public class Animal {
	public final void walk() {
		System.out.println("Animal walks ");
	}	
}

package com.demo;

public class Dog extends Animal{

	public final void walk() {
		System.out.println("Dog walks ");
	}
}

The above declaration will give this error in the Dog class Cannot override the final method from Animal

Final Variable

When a variable is declared final means its value can not be changed after its initialization. But it's not necessary to initialize variables at the time of declaration.

Example

package com.demo;

public class TestFinal {
	public static void main(String[] args) {
		final int count;
		count=9;
		System.out.println("Count is "+count++); // This will give error
	}	
}

Final Parameters

When we used final parameters in the method means we can not change its value inside the method.

Example

package com.demo;

public class TestFinal {
	public static void main(String[] args) {
		int count=0;
		printCount(count);
	}	
	
	static void printCount(final int count) {
		count=9;   // This will give error as we are changing value of final parameter count inside method 
		System.out.println(count);
	}
}

We have completed this article. Let me know if you have any questions.

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