Java Super Keyword explained

What is the Super Keyword?

Super keyword is used to access members of the superclass from the subclass. It can be used to access both instance fields and methods.

Code Sample

Consider the following code:

public class Base {    int a;  int b;    public void baseMethod() {    System.out.println("In base class method”);  }}public class Sub extends Base {    int c;    public void subMethod() {    super.a=4;    super.b=9;    super.baseMethod();    System.out.println("In sub class method");  }  }
  • There are 2 classes, Base and Sub
  • Sub is a sub-class of Base; it has a method called subMethod
  • The base fields a,b are accessed via the super keyword in subMethod
  • The base method baseMethod is also accessed via the super keyword

When this code is executed, it will print the following output:

In base class methodIn sub class method

Points to Remember

  • The super keyword is a bit redundant for instance fields and methods since as long as the instance fields and method of the superclass and not private, they can be accessed directly in the sub-class.
  • The super keyword is useful for accessing class members only when the base class has a member with the same name.
  • A subclass constructor can invoke a superclass constructor using the super keyword.

 

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