| /* |
| * Copyright 2001-2004 The Apache Software Foundation |
| * |
| * Licensed 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.collections; |
| |
| 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. |
| * |
| * @see java.util.Stack |
| * @since Commons Collections 1.0 |
| * @version $Revision: 1.1 $ $Date: 2009/05/27 22:16:19 $ |
| * |
| * @author Craig R. McClanahan |
| * @author Paul Jack |
| * @author Stephen Colebourne |
| */ |
| public class ArrayStack extends ArrayList implements Buffer { |
| |
| /** 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 BufferUnderflowException if the stack is empty |
| */ |
| public Object get() { |
| int size = size(); |
| if (size == 0) { |
| throw new BufferUnderflowException(); |
| } |
| return get(size - 1); |
| } |
| |
| /** |
| * Removes the element on the top of the stack. |
| * |
| * @return the removed element |
| * @throws BufferUnderflowException if the stack is empty |
| */ |
| public Object remove() { |
| int size = size(); |
| if (size == 0) { |
| throw new BufferUnderflowException(); |
| } |
| return remove(size - 1); |
| } |
| |
| } |