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org.apache.commons.collections

Class ArrayStack

ArrayList
|
+--org.apache.commons.collections.ArrayStack

All Implemented Interfaces:
Buffer


public class ArrayStack
extends ArrayList
implements Buffer

An implementation of the 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 remove() method removes them from the top down.

Unlike Stack, ArrayStack accepts null entries.

Since:
Commons Collections 1.0
Authors:
Craig R. McClanahan
Paul Jack
Stephen Colebourne
See Also:
java.util.Stack

Constructor Summary

ArrayStack()

Constructs a new empty ArrayStack.

ArrayStack(int initialSize)

Constructs a new empty ArrayStack with an initial size.

Method Summary

boolean

empty()

Return true if this stack is currently empty.

Object

get()

Returns the element on the top of the stack.

Object

peek()

Returns the top item off of this stack without removing it.

Object

peek(int n)

Returns the n'th item down (zero-relative) from the top of this stack without removing it.

Object

pop()

Pops the top item off of this stack and return it.

Object

push(Object item)

Pushes a new item onto the top of this stack.

Object

remove()

Removes the element on the top of the stack.

int

search(Object object)

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.

Constructor Details

ArrayStack

public ArrayStack()

Constructs a new empty ArrayStack. The initial size is controlled by ArrayList and is currently 10.


ArrayStack

public ArrayStack(int initialSize)

Constructs a new empty ArrayStack with an initial size.

Parameters:
initialSize - the initial size to use
Throws:
- if the specified initial size is negative

Method Details

empty

public boolean empty()

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.

Returns:
true if the stack is currently empty

get

public Object get()

Returns the element on the top of the stack.

Returns:
the element on the top of the stack
Throws:
BufferUnderflowException - if the stack is empty

peek

public Object peek()

Returns the top item off of this stack without removing it.

Returns:
the top item on the stack
Throws:
- if the stack is empty

peek

public Object peek(int n)

Returns the n'th item down (zero-relative) from the top of this stack without removing it.

Parameters:
n - the number of items down to go
Returns:
the n'th item on the stack, zero relative
Throws:
- if there are not enough items on the stack to satisfy this request

pop

public Object pop()

Pops the top item off of this stack and return it.

Returns:
the top item on the stack
Throws:
- if the stack is empty

push

public Object push(Object item)

Pushes a new item onto the top of this stack. The pushed item is also returned. This is equivalent to calling add.

Parameters:
item - the item to be added
Returns:
the item just pushed

remove

public Object remove()

Removes the element on the top of the stack.

Returns:
the removed element
Throws:
BufferUnderflowException - if the stack is empty

search

public int search(Object object)

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.

Parameters:
object - the object to be searched for
Returns:
the 1-based depth into the stack of the object, or -1 if not found