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Enable nulls to be added to the stack 

Add initial size constructor
Tidy javadoc and code layout


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130827 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne 2002-10-13 12:56:42 +00:00
parent 0f48820533
commit 3aba1278c3
1 changed files with 79 additions and 74 deletions
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153
src/java/org/apache/commons/collections/ArrayStack.java
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@ -1,7 +1,7 @@
/*
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/ArrayStack.java,v 1.9 2002/10/12 22:15:19 scolebourne Exp $
* $Revision: 1.9 $
* $Date: 2002/10/12 22:15:19 $
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/ArrayStack.java,v 1.10 2002/10/13 12:56:42 scolebourne Exp $
* $Revision: 1.10 $
* $Date: 2002/10/13 12:56:42 $
*
* ====================================================================
*
@ -58,174 +58,179 @@
* <http://www.apache.org/>.
*
*/
package org.apache.commons.collections;
import java.util.ArrayList;
import java.util.EmptyStackException;
/**
* An implementation of the {@link java.util.Stack} API that is based on an
* <code>ArrayList</code> instead of a <code>Vector</code>, 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 <Code>ArrayStack</Code> is based on insertion
* <p>
* The removal order of an <code>ArrayStack</code> is based on insertion
* order: The most recently added element is removed first. The iteration
* order is <I>not</I> the same as the removal order. The iterator returns
* order is <i>not</i> 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.
* <p>
* Unlike <code>Stack</code>, <code>ArrayStack</code> accepts null entries.
*
* @since 1.0
* @author Craig R. McClanahan
* @version $Revision: 1.9 $ $Date: 2002/10/12 22:15:19 $
* @author Paul Jack
* @author Stephen Colebourne
* @since 1.0
* @version $Id: ArrayStack.java,v 1.10 2002/10/13 12:56:42 scolebourne Exp $
* @see java.util.Stack
*/
public class ArrayStack extends ArrayList implements Buffer {
final private static long serialVersionUID = 2130079159931574599L;
//, local class serialVersionUID = -3491241305852305742
/**
* Constructs a new empty <Code>ArrayStack</Code>.
* Constructs a new empty <code>ArrayStack</code>. The initial size
* is controlled by <code>ArrayList</code> and is currently 10.
*/
public ArrayStack() {
super();
}
// --------------------------------------------------------- Public Methods
/**
* Constructs a new empty <code>ArrayStack</code> 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 <code>true</code> if this stack is currently empty.
* <p>
* This method exists for compatability with <code>java.util.Stack</code>.
* New users of this class should use <code>isEmpty</code> instead.
*
* @return true if the stack is currently empty
*/
public boolean empty() {
return (size() == 0);
return isEmpty();
}
/**
* Return the top item off of this stack without removing it.
* Returns the top item off of this stack without removing it.
*
* @exception EmptyStackExceptino if the stack is empty
* @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)
if (n <= 0) {
throw new EmptyStackException();
else
return (get(n - 1));
} else {
return get(n - 1);
}
}
/**
* Return the n'th item down (zero-relative) from the top of this
* Returns the n'th item down (zero-relative) from the top of this
* stack without removing it.
*
* @param n Number of items down to go
*
* @exception EmptyStackException if there are not enough items on the
* @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)
if (m < 0) {
throw new EmptyStackException();
else
return (get(m));
} else {
return get(m);
}
}
/**
* Pop the top item off of this stack and return it.
* Pops the top item off of this stack and return it.
*
* @exception EmptyStackException if the stack is empty
* @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)
if (n <= 0) {
throw new EmptyStackException();
else
return (remove(n - 1));
} else {
return remove(n - 1);
}
}
/**
* Push a new item onto the top of this stack. The pushed item is also
* returned.
* Pushes a new item onto the top of this stack. The pushed item is also
* returned. This is equivalent to calling <code>add</code>.
*
* @param item Item to be added
* @param item the item to be added
* @return the item just pushed
*/
public Object push(Object item) {
if (item == null)
throw new NullPointerException();
add(item);
return (item);
return item;
}
/**
* Return the one-based position of the distance from the top that the
* 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 <code>1</code>. If the object is not
* present on the stack, return <code>-1</code> instead. The
* <code>equals()</code> method is used to compare to the items
* in this stack.
*
* @param o Object to be searched for
* @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 o) {
public int search(Object object) {
int i = size() - 1; // Current index
int n = 1; // Current distance
while (i >= 0) {
if (o.equals(get(i)))
return (n);
Object current = get(i);
if ((object == null && current == null) ||
(object != null && object.equals(current))) {
return n;
}
i--;
n++;
}
return (-1);
return -1;
}
/**
* Returns the element on the top of the stack.
* Returns the element on the top of the stack.
*
* @return the element on the top of the stack
* @throws BufferUnderflowException if the stack is empty
* @return the element on the top of the stack
* @throws BufferUnderflowException if the stack is empty
*/
public Object get() {
int size = size();
if (size == 0) throw new BufferUnderflowException();
if (size == 0) {
throw new BufferUnderflowException();
}
return get(size - 1);
}
/**
* Removes the element on the top of the stack.
* Removes the element on the top of the stack.
*
* @return the removed element
* @throws BufferUnderflowException if the stack is empty
* @return the removed element
* @throws BufferUnderflowException if the stack is empty
*/
public Object remove() {
int size = size();
if (size == 0) throw new BufferUnderflowException();
if (size == 0) {
throw new BufferUnderflowException();
}
return remove(size - 1);
}