org.apache.axis2.util.ArrayStack Maven / Gradle / Ivy
/*
* 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 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, whereas the {@link #remove()} method removes
* them from the top down.
*
* Unlike Stack, ArrayStack accepts null entries.
*/
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(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 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 add.
*
* @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 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(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);
}
}