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package java.util;

public

class Stack<E> extends Vector<E> {

/**

* Creates an empty Stack.

*/

public Stack() {

}

/**

* Pushes an item onto the top of this stack. This has exactly

* the same effect as:

* <blockquote><pre>

* addElement(item)</pre></blockquote>

*

* @param item the item to be pushed onto this stack.

* @return the <code>item</code> argument.

* @see java.util.Vector#addElement

*/

public E push(E item) {

addElement(item);

return item;

}

/**

* Removes the object at the top of this stack and returns that

* object as the value of this function.

*

* @return The object at the top of this stack (the last item

* of the <tt>Vector</tt> object).

* @throws EmptyStackException if this stack is empty.

*/

public synchronized E pop() {

E obj;

int len = size();

obj = peek();

removeElementAt(len - 1);

return obj;

}

/**

* Looks at the object at the top of this stack without removing it

* from the stack.

*

* @return the object at the top of this stack (the last item

* of the <tt>Vector</tt> object).

* @throws EmptyStackException if this stack is empty.

*/

public synchronized E peek() {

int len = size();

if (len == 0)

throw new EmptyStackException();

return elementAt(len - 1);

}

/**

* Tests if this stack is empty.

*

* @return <code>true</code> if and only if this stack contains

* no items; <code>false</code> otherwise.

*/

public boolean empty() {

return size() == 0;

}

/**

* Returns the 1-based position where an object is on this stack.

* If the object <tt>o</tt> occurs as an item in this stack, this

* method returns the distance from the top of the stack of the

* occurrence nearest the top of the stack; the topmost item on the

* stack is considered to be at distance <tt>1</tt>. The <tt>equals</tt>

* method is used to compare <tt>o</tt> to the

* items in this stack.

*

* @param o the desired object.

* @return the 1-based position from the top of the stack where

* the object is located; the return value <code>-1</code>

* indicates that the object is not on the stack.

*/

public synchronized int search(Object o) {

int i = lastIndexOf(o);

if (i >= 0) {

return size() - i;

}

return -1;

}

/** use serialVersionUID from JDK 1.0.2 for interoperability */

private static final long serialVersionUID = 1224463164541339165L;

}