The final keyword is used for many purposes. The different use of final keyword is shown with sample program below.
Final Variable
A final variable can not be updated. Generally, final variables are used where the values remain unchnaged throughout the application. For example, the value of Pi that does not change.
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public class A {
final int f = 0;
}
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public class Test {
public static void main(String[] args) {
A a = new A();
//a.f = 10; // final variable can not be assigned by any value after declaration
System.out.println(a.f);
}
}
Final Method
Final methods can not be overwritten. Hence, if you define a method that can not be overwritten in sub-class, the method should be declared as final method.
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public class A {
int x = 10;
final void print() {
System.out.println(x);
}
}
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public class B extends A {
int y = 5;
//void print() {
// System.out.println(x + y);
//}
}
Final Class
If a class is declared as final, the class can not be inherited.
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final public class A {
int x = 10;
void print() {
System.out.println(x);
}
}
The following class will not compile, as the class B inherits class A, which is final.
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public class B extends A {
}
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