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final keyword

In this chapter you will learn:

  1. What are final variables
  2. How to use final to prevent overriding

Final variables

A final variable cannot be modified. You must initialize a final variable when it is declared. A final variable is essentially a constant.

public class Main {
  final int FILE_NEW = 1;
  final int FILE_OPEN = 2;
}

Prevent overriding

Methods declared as final cannot be overridden. 

class Base {//from   ja v  a2  s.c o m
  final void meth() {
    System.out.println("This is a final method.");
  }
}

class B extends A {
  void meth() { // ERROR! Can't override.

    System.out.println("Illegal!");

  }
}

If you try to compile the code above, the following error will be generated by the compiler.

Next chapter...

What you will learn in the next chapter:

  1. What is abstract class
  2. How to create abstract class
  3. A demo for using abstract methods and classes
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