142 lines
4.6 KiB
Java
142 lines
4.6 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.tomcat.util.digester;
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import java.util.ArrayList;
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import java.util.EmptyStackException;
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/**
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* <p>Imported copy of the <code>ArrayStack</code> class from
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* Commons Collections, which was the only direct dependency from Digester.</p>
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*
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* <p><strong>WARNNG</strong> - This class is public solely to allow it to be
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* used from subpackages of <code>org.apache.commons.digester</code>.
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* It should not be considered part of the public API of Commons Digester.
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* If you want to use such a class yourself, you should use the one from
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* Commons Collections directly.</p>
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*
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* <p>An implementation of the {@link java.util.Stack} API that is based on an
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* <code>ArrayList</code> instead of a <code>Vector</code>, so it is not
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* synchronized to protect against multi-threaded access. The implementation
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* is therefore operates faster in environments where you do not need to
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* worry about multiple thread contention.</p>
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*
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* <p>Unlike <code>Stack</code>, <code>ArrayStack</code> accepts null entries.
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* </p>
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*
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* @param <E> Type of object in this stack
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*
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* @see java.util.Stack
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* @since Digester 1.6 (from Commons Collections 1.0)
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*/
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public class ArrayStack<E> extends ArrayList<E> {
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/** Ensure serialization compatibility */
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private static final long serialVersionUID = 2130079159931574599L;
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/**
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* Constructs a new empty <code>ArrayStack</code>. The initial size
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* is controlled by <code>ArrayList</code> and is currently 10.
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*/
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public ArrayStack() {
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super();
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}
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/**
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* Constructs a new empty <code>ArrayStack</code> with an initial size.
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*
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* @param initialSize the initial size to use
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* @throws IllegalArgumentException if the specified initial size
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* is negative
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*/
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public ArrayStack(int initialSize) {
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super(initialSize);
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}
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/**
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* Return <code>true</code> if this stack is currently empty.
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* <p>
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* This method exists for compatibility with <code>java.util.Stack</code>.
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* New users of this class should use <code>isEmpty</code> instead.
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*
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* @return true if the stack is currently empty
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*/
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public boolean empty() {
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return isEmpty();
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}
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/**
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* Returns the top item off of this stack without removing it.
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*
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* @return the top item on the stack
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* @throws EmptyStackException if the stack is empty
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*/
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public E peek() throws EmptyStackException {
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int n = size();
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if (n <= 0) {
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throw new EmptyStackException();
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} else {
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return get(n - 1);
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}
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}
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/**
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* Returns the n'th item down (zero-relative) from the top of this
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* stack without removing it.
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*
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* @param n the number of items down to go
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* @return the n'th item on the stack, zero relative
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* @throws EmptyStackException if there are not enough items on the
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* stack to satisfy this request
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*/
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public E peek(int n) throws EmptyStackException {
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int m = (size() - n) - 1;
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if (m < 0) {
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throw new EmptyStackException();
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} else {
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return get(m);
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}
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}
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/**
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* Pops the top item off of this stack and return it.
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*
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* @return the top item on the stack
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* @throws EmptyStackException if the stack is empty
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*/
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public E pop() throws EmptyStackException {
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int n = size();
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if (n <= 0) {
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throw new EmptyStackException();
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} else {
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return remove(n - 1);
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}
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}
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/**
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* Pushes a new item onto the top of this stack. The pushed item is also
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* returned. This is equivalent to calling <code>add</code>.
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*
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* @param item the item to be added
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* @return the item just pushed
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*/
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public E push(E item) {
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add(item);
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return item;
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}
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}
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