Instance variable as final in Java

final is a non-access modifier for Java elements. The final modifier is used for finalizing the implementations of classes, methods, and variables. A final instance variable can be explicitly initialized only once.

A final instance variable should be initialized at one of the following occasions −

• At time of declaration.

• In constructor.

• In instance block.

Compiler will throw error, it a final variable is not initialized at all using any of the above methods. Following examples showcases example of instance variables as final.

Example

 Live Demo

public class Tester{    final int A = 1;    final int B;{       B = 2;    }    final int C;    Tester(){       C = 3;    }    public static void main(String[] args) {       Tester t = new Tester();       System.out.println("A = " + t.A + ", B = " + t.B + ", C = " + t.C);    } }

Output

A = 1, B = 2, C = 3