Java Programming/Keywords/super

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super is a keyword.

  • It is used inside a sub-class method definition to call a method defined in the super class. Private methods of the super-class cannot be called. Only public and protected methods can be called by the super keyword.
  • It is also used by class constructors to invoke constructors of its parent class.



For example:

Computer code Code listing 1:
  1. public class SuperClass {
  2.    public void printHello() {
  3.       System.out.println("Hello from SuperClass");
  4.       return;
  5.    }
  6. }
Computer code Code listing 2:
  1. public class SubClass extends SuperClass {
  2.    public void printHello() {
  3.       super.printHello();
  4.       System.out.println("Hello from SubClass");
  5.       return;
  6.    }
  7.    public static main(String[] args) {
  8.       SubClass obj = new SubClass();
  9.       obj.printHello();
  10.    }
  11. }

Running the above program:

Computer code Command for Code listing 2
$Java SubClass
Computer code Output of Code listing 2
Hello from SuperClass
Hello from SubClass

In Java 1.5 and later, the "super" keyword is also used to specify a lower bound on a wildcard type parameter in Generics.

Example Code section 1: A lower bound on a wildcard type parameter.
  1. public void sort(Comparator<? super T> comp) {
  2.   ...
  3. }

See also: