Package org.apache.commons.collections

Class ArrayStack

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractList<E>
java.util.ArrayList
org.apache.commons.collections.ArrayStack
All Implemented Interfaces:
Serializable, Cloneable, Iterable, Collection, List, RandomAccess, Buffer
public class ArrayStack extends ArrayList implements Buffer
An implementation of the 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
Version:
$Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
Author:
Craig R. McClanahan, Paul Jack, Stephen Colebourne
See Also:

  • 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:
      IllegalArgumentException - 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

    • peek

      public Object peek() throws EmptyStackException
      Returns the top item off of this stack without removing it.
      Returns:
      the top item on the stack
      Throws:
      EmptyStackException - if the stack is empty

    • peek

      public Object peek(int n) throws EmptyStackException
      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:
      EmptyStackException - if there are not enough items on the stack to satisfy this request

    • pop

      public Object pop() throws EmptyStackException
      Pops the top item off of this stack and return it.
      Returns:
      the top item on the stack
      Throws:
      EmptyStackException - 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

    • 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

    • get

      public Object get()
      Returns the element on the top of the stack.
      Specified by:
      get in interface Buffer
      Returns:
      the element on the top of the stack
      Throws:
      BufferUnderflowException - if the stack is empty

    • remove

      public Object remove()
      Removes the element on the top of the stack.
      Specified by:
      remove in interface Buffer
      Returns:
      the removed element
      Throws:
      BufferUnderflowException - if the stack is empty