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When Not to Use Inheritance

• Java standard library:
  

  public class Stack extends Vector // DON'T
  {
     Object pop() { ... }
     void push(Object item) { ... }
     ...
  }
  

• Bad idea: Inherit all Vector methods
• Can insert/remove in the middle of the stack
• Remedy: Use aggregation
  

  public class Stack
  {
     ...
     private Vector elements;
  }
  

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