org.eclipse.aether.util.graph.visitor.Stack Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2010, 2012 Sonatype, Inc.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Sonatype, Inc. - initial API and implementation
*******************************************************************************/
package org.eclipse.aether.util.graph.visitor;
import java.util.AbstractList;
import java.util.NoSuchElementException;
import java.util.RandomAccess;
/**
* A non-synchronized stack with a non-modifiable list view which starts at the top of the stack. While
* {@code LinkedList} can provide the same behavior, it creates many temp objects upon frequent pushes/pops.
*/
class Stack
extends AbstractList
implements RandomAccess
{
@SuppressWarnings( "unchecked" )
private E[] elements = (E[]) new Object[96];
private int size;
public void push( E element )
{
if ( size >= elements.length )
{
@SuppressWarnings( "unchecked" )
E[] tmp = (E[]) new Object[size + 64];
System.arraycopy( elements, 0, tmp, 0, elements.length );
elements = tmp;
}
elements[size++] = element;
}
public E pop()
{
if ( size <= 0 )
{
throw new NoSuchElementException();
}
return elements[--size];
}
public E peek()
{
if ( size <= 0 )
{
return null;
}
return elements[size - 1];
}
@Override
public E get( int index )
{
if ( index < 0 || index >= size )
{
throw new IndexOutOfBoundsException( "Index: " + index + ", Size: " + size );
}
return elements[size - index - 1];
}
@Override
public int size()
{
return size;
}
}