A faster, smaller stack implementation.
/*
* 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.
*/
import java.util.ArrayList;
import java.util.Collection;
import java.util.EmptyStackException;
/**
* A faster, smaller stack implementation. ArrayListStack is final and unsynchronized (the JDK's
* methods are synchronized). In addition you can set the initial capacity if you want via the
* ArrayListStack(int) constructor.
*
* @author Jonathan Locke
* @param <T>
*/
public final class ArrayListStack<T> extends ArrayList<T>
{
private static final long serialVersionUID = 1L;
/**
* Construct.
*
* @param initialCapacity
* Initial capacity of the stack
*/
public ArrayListStack(final int initialCapacity)
{
super(initialCapacity);
}
/**
* Construct.
*/
public ArrayListStack()
{
this(10);
}
/**
* Construct.
*
* @param collection
* The collection to add
*/
public ArrayListStack(final Collection<T> collection)
{
super(collection);
}
/**
* Pushes an item onto the top of this stack.
*
* @param item
* the item to be pushed onto this stack.
*/
public final void push(final T item)
{
add(item);
}
/**
* Removes the object at the top of this stack and returns that object.
*
* @return The object at the top of this stack
* @exception EmptyStackException
* If this stack is empty.
*/
public final T pop()
{
final T top = peek();
remove(size() - 1);
return top;
}
/**
* Looks at the object at the top of this stack without removing it.
*
* @return The object at the top of this stack
* @exception EmptyStackException
* If this stack is empty.
*/
public final T peek()
{
int size = size();
if (size == 0)
{
throw new EmptyStackException();
}
return get(size - 1);
}
/**
* Tests if this stack is empty.
*
* @return <code>true</code> if and only if this stack contains no items; <code>false</code>
* otherwise.
*/
public final boolean empty()
{
return size() == 0;
}
/**
* Returns the 1-based position where an object is on this stack. If the object <tt>o</tt>
* occurs as an item in this stack, this method returns the distance from the top of the stack
* of the occurrence nearest the top of the stack; the topmost item on the stack is considered
* to be at distance <tt>1</tt>. The <tt>equals</tt> method is used to compare <tt>o</tt>
* to the items in this stack.
*
* @param o
* the desired object.
* @return the 1-based position from the top of the stack where the object is located; the
* return value <code>-1</code> indicates that the object is not on the stack.
*/
public final int search(final T o)
{
int i = lastIndexOf(o);
if (i >= 0)
{
return size() - i;
}
return -1;
}
}
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