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Java Source | 1998-09-22 | 2.7 KB | 106 lines |
- /*
- * @(#)Stack.java 1.17 98/07/01
- *
- * Copyright 1995-1998 by Sun Microsystems, Inc.,
- * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
- * All rights reserved.
- *
- * This software is the confidential and proprietary information
- * of Sun Microsystems, Inc. ("Confidential Information"). You
- * shall not disclose such Confidential Information and shall use
- * it only in accordance with the terms of the license agreement
- * you entered into with Sun.
- */
-
- package java.util;
-
- /**
- * The <code>Stack</code> class represents a last-in-first-out
- * (LIFO) stack of objects.
- *
- * @author Jonathan Payne
- * @version 1.17, 07/01/98
- * @since JDK1.0
- */
- public
- class Stack extends Vector {
- /**
- * Pushes an item onto the top of this stack.
- *
- * @param item the item to be pushed onto this stack.
- * @return the <code>item</code> argument.
- * @since JDK1.0
- */
- public Object push(Object 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.
- * @exception EmptyStackException if this stack is empty.
- * @since JDK1.0
- */
- public synchronized Object pop() {
- Object 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.
- * @exception EmptyStackException if this stack is empty.
- * @since JDK1.0
- */
- public synchronized Object 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 this stack is empty;
- * <code>false</code> otherwise.
- * @since JDK1.0
- */
- public boolean empty() {
- return size() == 0;
- }
-
- /**
- * Returns where an object is on this stack.
- *
- * @param o the desired object.
- * @return the distance 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.
- * @since JDK1.0
- */
- 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;
- }
-