A very simple unsynchronized stack. This one is faster than the java.util-Version.
/**
*
* JCommon : a free Java report library
*
*
* Project Info: http://www.jfree.org/jcommon/
*
* (C) Copyright 2000-2006, by Object Refinery Limited and Contributors.
*
* This library is free software; you can redistribute it and/or modify it under the terms
* of the GNU Lesser General Public License as published by the Free Software Foundation;
* either version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License along with this
* library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307, USA.
*
* [Java is a trademark or registered trademark of Sun Microsystems, Inc.
* in the United States and other countries.]
*
* ------------
* $Id: FastStack.java,v 1.3 2008/09/10 09:22:05 mungady Exp $
* ------------
* (C) Copyright 2002-2006, by Object Refinery Limited.
*/
import java.io.Serializable;
import java.util.Arrays;
import java.util.EmptyStackException;
/**
* A very simple unsynchronized stack. This one is faster than the
* java.util-Version.
*
* @author Thomas Morgner
*/
public final class FastStack implements Serializable, Cloneable {
private Object[] contents;
private int size;
private int initialSize;
/**
* Creates a new empty stack.
*/
public FastStack() {
this.initialSize = 10;
}
/**
* Creates a new empty stack with the specified initial storage size.
*
* @param size
* the initial storage elements.
*/
public FastStack(int size) {
this.initialSize = Math.max(1, size);
}
/**
* Returns <code>true</code> if the stack is empty, and <code>false</code>
* otherwise.
*
* @return A boolean.
*/
public boolean isEmpty() {
return this.size == 0;
}
/**
* Returns the number of elements in the stack.
*
* @return The element count.
*/
public int size() {
return this.size;
}
/**
* Pushes an object onto the stack.
*
* @param o
* the object.
*/
public void push(Object o) {
if (this.contents == null) {
this.contents = new Object[this.initialSize];
this.contents[0] = o;
this.size = 1;
return;
}
final int oldSize = this.size;
this.size += 1;
if (this.contents.length == this.size) {
// grow ..
final Object[] newContents = new Object[this.size + this.initialSize];
System.arraycopy(this.contents, 0, newContents, 0, this.size);
this.contents = newContents;
}
this.contents[oldSize] = o;
}
/**
* Returns the object at the top of the stack without removing it.
*
* @return The object at the top of the stack.
*/
public Object peek() {
if (this.size == 0) {
throw new EmptyStackException();
}
return this.contents[this.size - 1];
}
/**
* Removes and returns the object from the top of the stack.
*
* @return The object.
*/
public Object pop() {
if (this.size == 0) {
throw new EmptyStackException();
}
this.size -= 1;
final Object retval = this.contents[this.size];
this.contents[this.size] = null;
return retval;
}
/**
* Returns a clone of the stack.
*
* @return A clone.
*/
public Object clone() {
try {
FastStack stack = (FastStack) super.clone();
if (this.contents != null) {
stack.contents = (Object[]) this.contents.clone();
}
return stack;
} catch (CloneNotSupportedException cne) {
throw new IllegalStateException("Clone not supported? Why?");
}
}
/**
* Clears the stack.
*/
public void clear() {
this.size = 0;
if (this.contents != null) {
Arrays.fill(this.contents, null);
}
}
/**
* Returns the item at the specified slot in the stack.
*
* @param index
* the index.
*
* @return The item.
*/
public Object get(final int index) {
if (index >= this.size) {
throw new IndexOutOfBoundsException();
}
return this.contents[index];
}
}
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