How many ways are there to initialize a final variable in java?

In Java, final is the access modifier which can be used with a filed, class and a method.

• When a method if final it cannot be overridden.
• When a variable is final its value cannot be modified further.
• When a class is final it cannot be extended.

Initializing a final variable

Once you declare a final variable, it is a must to initialize it. You can initialize the final instance variable −

• At the time of declaration as.

public final String name = "Raju";
public final int age = 20;

• Within an instance (non-static) block.

{
   this.name = "Raju";
   this.age = 20;
}

• Within a default constructor.

public final String name;
public final int age;
public Student(){
   this.name = "Raju";
   this.age = 20;
}

Note − If you try to initialize the final instance variable elsewhere, a compile-time error will be generated.

Example1: At the time of declaration

In the following Java program, the class Student contains two final variables − name, age and, we are initializing them at the time of declaration −

 Live Demo

public class Student {
   public final String name = "Raju";
   public final int age = 20;
   public void display(){
      System.out.println("Name of the Student: "+this.name );
      System.out.println("Age of the Student: "+this.age );
   }
   public static void main(String args[]) {
      new Student().display();
   }
}

Output

Name of the Student: Raju
Age of the Student: 20

Example2: within an instance block

In the following Java program, the class Student contains two final variables− name, age and, we are initializing them within an instance block −

 Live Demo

public class Student {
   public final String name;
   public final int age; {
      this.name = "Raju";
      this.age = 20;
   }
   public void display(){
      System.out.println("Name of the Student: "+this.name );
      System.out.println("Age of the Student: "+this.age );
   }
   public static void main(String args[]) {
      new Student().display();
   }
}

Output

Name of the Student: Raju
Age of the Student: 20

Example3: within the default constructor

In the following Java program, the class Student contains two final variables − name, age and, we are initializing them within a default constructor −

 Live Demo

public class Student {
   public final String name;
   public final int age;
   public Student(){
      this.name = "Raju";
      this.age = 20;
   }
   public void display(){
      System.out.println("Name of the Student: "+this.name );
      System.out.println("Age of the Student: "+this.age );
   }
   public static void main(String args[]) {
      new Student().display();
   }
}

Output

Name of the Student: Raju
Age of the Student: 20