| /* |
| * 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.axis2.util; |
| |
| import java.util.ArrayList; |
| import java.util.EmptyStackException; |
| |
| /** |
| * An implementation of the {@link java.util.Stack} API that is based on an <code>ArrayList</code> |
| * instead of a <code>Vector</code>, 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. |
| * <p/> |
| * The removal order of an <code>ArrayStack</code> is based on insertion order: The most recently |
| * added element is removed first. The iteration order is <i>not</i> the same as the removal order. |
| * The iterator returns elements from the bottom up, whereas the {@link #remove()} method removes |
| * them from the top down. |
| * <p/> |
| * Unlike <code>Stack</code>, <code>ArrayStack</code> accepts null entries. |
| */ |
| public class ArrayStack extends ArrayList { |
| |
| /** Ensure serialization compatibility */ |
| private static final long serialVersionUID = 2130079159931574599L; |
| |
| /** |
| * Constructs a new empty <code>ArrayStack</code>. The initial size is controlled by |
| * <code>ArrayList</code> and is currently 10. |
| */ |
| public ArrayStack() { |
| super(); |
| } |
| |
| /** |
| * Constructs a new empty <code>ArrayStack</code> with an initial size. |
| * |
| * @param initialSize the initial size to use |
| * @throws IllegalArgumentException if the specified initial size is negative |
| */ |
| public ArrayStack(int initialSize) { |
| super(initialSize); |
| } |
| |
| /** |
| * Return <code>true</code> if this stack is currently empty. |
| * <p/> |
| * This method exists for compatibility with <code>java.util.Stack</code>. New users of this |
| * class should use <code>isEmpty</code> 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 Object peek() throws EmptyStackException { |
| 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 Object peek(int n) throws EmptyStackException { |
| 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 Object pop() throws EmptyStackException { |
| 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 <code>add</code>. |
| * |
| * @param item the item to be added |
| * @return the item just pushed |
| */ |
| public Object push(Object 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 <code>1</code>. If |
| * the object is not present on the stack, return <code>-1</code> instead. The |
| * <code>equals()</code> 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(Object object) { |
| int i = size() - 1; // Current index |
| int n = 1; // Current distance |
| while (i >= 0) { |
| Object current = get(i); |
| if ((object == null && current == null) || |
| (object != null && object.equals(current))) { |
| return n; |
| } |
| i--; |
| n++; |
| } |
| return -1; |
| } |
| |
| /** |
| * Returns the element on the top of the stack. |
| * |
| * @return the element on the top of the stack |
| * @throws EmptyStackException if the stack is empty |
| */ |
| public Object get() { |
| int size = size(); |
| if (size == 0) { |
| throw new EmptyStackException(); |
| } |
| return get(size - 1); |
| } |
| |
| /** |
| * Removes the element on the top of the stack. |
| * |
| * @return the removed element |
| * @throws EmptyStackException if the stack is empty |
| */ |
| public Object remove() { |
| int size = size(); |
| if (size == 0) { |
| throw new EmptyStackException(); |
| } |
| return remove(size - 1); |
| } |
| |
| } |