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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.collections4;

import java.util.ArrayList;
import java.util.EmptyStackException;

/**
 * An implementation of the {@link java.util.Stack} API that is based on an
 * ArrayList instead of a Vector, so it is not
 * synchronized to protect against multi-threaded access.  The implementation
 * is therefore operates faster in environments where you do not need to
 * worry about multiple thread contention.
 * 

* The removal order of an ArrayStack is based on insertion * order: The most recently added element is removed first. The iteration * order is not the same as the removal order. The iterator returns * elements from the bottom up. *

* Unlike Stack, ArrayStack accepts null entries. *

* Note: From version 4.0 onwards, this class does not implement the * removed {@code Buffer} interface anymore. * * @see java.util.Stack * @since 1.0 * @version $Id: ArrayStack.java 1477779 2013-04-30 18:55:24Z tn $ * @deprecated use {@link java.util.ArrayDeque} instead (available from Java 1.6) */ @Deprecated public class ArrayStack extends ArrayList { /** Ensure serialization compatibility */ private static final long serialVersionUID = 2130079159931574599L; /** * Constructs a new empty ArrayStack. The initial size * is controlled by ArrayList and is currently 10. */ public ArrayStack() { super(); } /** * Constructs a new empty ArrayStack with an initial size. * * @param initialSize the initial size to use * @throws IllegalArgumentException if the specified initial size * is negative */ public ArrayStack(final int initialSize) { super(initialSize); } /** * Return true if this stack is currently empty. *

* This method exists for compatibility with java.util.Stack. * New users of this class should use isEmpty instead. * * @return true if the stack is currently empty */ public boolean empty() { return isEmpty(); } /** * Returns the top item off of this stack without removing it. * * @return the top item on the stack * @throws EmptyStackException if the stack is empty */ public E peek() throws EmptyStackException { final int n = size(); if (n <= 0) { throw new EmptyStackException(); } else { return get(n - 1); } } /** * Returns the n'th item down (zero-relative) from the top of this * stack without removing it. * * @param n the number of items down to go * @return the n'th item on the stack, zero relative * @throws EmptyStackException if there are not enough items on the * stack to satisfy this request */ public E peek(final int n) throws EmptyStackException { final int m = (size() - n) - 1; if (m < 0) { throw new EmptyStackException(); } else { return get(m); } } /** * Pops the top item off of this stack and return it. * * @return the top item on the stack * @throws EmptyStackException if the stack is empty */ public E pop() throws EmptyStackException { final int n = size(); if (n <= 0) { throw new EmptyStackException(); } else { return remove(n - 1); } } /** * Pushes a new item onto the top of this stack. The pushed item is also * returned. This is equivalent to calling add. * * @param item the item to be added * @return the item just pushed */ public E push(final E item) { add(item); return item; } /** * Returns the one-based position of the distance from the top that the * specified object exists on this stack, where the top-most element is * considered to be at distance 1. If the object is not * present on the stack, return -1 instead. The * equals() method is used to compare to the items * in this stack. * * @param object the object to be searched for * @return the 1-based depth into the stack of the object, or -1 if not found */ public int search(final Object object) { int i = size() - 1; // Current index int n = 1; // Current distance while (i >= 0) { final Object current = get(i); if ((object == null && current == null) || (object != null && object.equals(current))) { return n; } i--; n++; } return -1; } }





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