Java – Final Modifier

final:

• Final is a keyword/modifier.
• A member become constant if we define it as final hence cannot be modified.
• We can apply final to Class or Method or Variable.

If Class is final, cannot be inherited:

final class A {             // logic } class B extends A  /* Error: final class-A cannot be extended */ {                       // logic }

If Method is final, cannot be overridden:

class A {             void m1(){                         …             }             final void m2(){                         …             } }

class B extends A {             void m1(){                         …             }             void m2(){   /* Error : */                         …             } }

If the variable is final become constant and cannot be modified:

class Test {             static final double PI = 3.142 ;             public static void main(String[] args) {                         Test.PI = 3.1412 ; // Error : can’t modify             } }

Why constructor cannot be final?

• final is used for fixing, avoid overriding and inheriting.
• Constructor cannot be final, because it can’t be inherited/overridden.