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package concurrency.composingobjects;

import java.util.Vector;

/**

* Extending vector to have a put-if-absent method

*

* Extension is more fragile than adding code directly to a class, because the

* implementation of the synchronization policy is now distributed over

* multiple, separately maintained source files. If the underlying class

* were to change its synchronization policy by choosing a different lock

* to guard its state variables, the subclass would subtly and silently

* break, because it no longer used the right lock to control

* concurrent access to the base class state. (The synchronization policy

* of Vector is fixed by its specification, so BetterVector would not suffer

* from this problem.)

*

* @author vijay

*/

public class BetterVector<E> extends Vector<E>{

public synchronized void putIfAbsent(E e){

if(!contains(e)){

add(e);

}

}

}