If your method has the same name that the parent’s, parameters and return type, you’re overriding it.
Also you can add @Override annotation on the top of your method.  
Always check parent’s method is not final nor private.
For instance
public class Parent{
  public void method(String param){
    //Do stuff
  }
  private void notExtendable(String param){
  }
  protected void alsoExtendable(String param){
  }
}
public class SubClass extends Parent{
  @Override
  public void method(String param){
    //super.method() //if you want to execute parent's method
    //Do your own stuff
  }
}
You have all information you need here: http://docs.oracle.com/javase/tutorial/java/IandI/override.html
solved How do I override a parent class’s method? [closed]