Java Programming/Keywords/super

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.
  • Super keyword are not used in static Method.

Syntax:

super.<method-name>([zero or more arguments]);

or:

super([zero or more arguments]);

For example:

Computer code Code listing 1: SuperClass.java
public class SuperClass {
   public void printHello() {
      System.out.println("Hello from SuperClass");
      return;
   }
}
Computer code Code listing 2: SubClass.java
public class SubClass extends SuperClass {
   public void printHello() {
      super.printHello();
      System.out.println("Hello from SubClass");
      return;
   }
   public static main(String[] args) {
      SubClass obj = new SubClass();
      obj.printHello();
   }
}

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.
public void sort(Comparator<? super T> comp) {
  ...
}

See also: