Access-Specifier and Method overriding

Posted on 01/08/2012 by Admin

We have 4 access-specifier.The following sequence represents the heirarchy from weakest/less restrictive access specifier to strongest/more restrictive access specifier

• public
• protected
• no-access or default
• private

If super class method is public,while overriding it in child class,it should be public,Since it is the weakest access specifier or least restrictive access specifier


OverrideTest.java

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class Demo {     public void sayHello()     {         System.out.println("Demo:sayHello()");     } }   public class OverrideTest extends Demo {     public void sayHello()//cannot be declared private,protected,no access     {         System.out.println("OverrideTest:sayHello()");     } }

If super class method is protected,while overriding it in child class,it can be public or protected but not anything else

OverrideTest.java

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class Demo {  protected void sayHello()  {   System.out.println("Demo:sayHello()");  } }   public class OverrideTest extends Demo {  public void sayHello()//can be public,protected But not anything else  {   System.out.println("OverrideTest:sayHello()");  } }

 If superclass method is default,then while overriding it in child class,it can be public,protected or no access,but cannot be private.

 OverrideTest.java

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class Demo {  void sayHello() //default access specifier  {   System.out.println("Demo:sayHello()");  } }   public class OverrideTest extends Demo {  protected void sayHello()//can be public,protected,default But not private  {   System.out.println("OverrideTest:sayHello()");  } }

 If superclass method is private,then while overriding it in child class,it can be anything. Since private method cannot be overrided.

OverrideTest.java

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class Demo {  private void sayHello() //cannot be overrided  {   System.out.println("Demo:sayHello()");  } }   public class OverrideTest extends Demo {  public void sayHello()//this is separate method,which can be overrided later by its subclass  {   System.out.println("OverrideTest:sayHello()");  } }