Inheritance for reuse

• Breaks encapsulation and liskov subsitution

  • See example of Stack inheriting from Vector in Java

• Always refactor to use a wrapper pattern (adpater or decorator)

How it works

• A subclass inherits from a class to inherit the behaviours that it can use in it's own new behaviour

  public class Stack<E> extends Vector<E> {
  
  public boolean empty() {
    return size() == 0;
  }
  
  public void push(E item) {
    add(item);
  }
  
  public E pop() {
    return remove(size()-1);
  }
  }

Issues

• Using an instance of the subclass, also has access to the methods of the super class

  • This can lead to the client using the subclass in ways it was not meant to be use, and possibly causing breaking behaviour