Package org.apache.commons.collections

Class 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:
    Stack, Serialized Form

    • Constructor Detail

      • 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 Detail

      • 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​(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

      • 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