Package org.apache.commons.collections

Class ArrayStack

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable, java.lang.Iterable, java.util.Collection, java.util.List, java.util.RandomAccess, Buffer
    public class ArrayStack
extends java.util.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
    See Also:
    Stack, Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      ArrayStack()
      Constructs a new empty ArrayStack.
      ArrayStack​(int initialSize)
      Constructs a new empty ArrayStack with an initial size.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean empty()
      Return true if this stack is currently empty.
      java.lang.Object get()
      Returns the element on the top of the stack.
      java.lang.Object peek()
      Returns the top item off of this stack without removing it.
      java.lang.Object peek​(int n)
      Returns the n'th item down (zero-relative) from the top of this stack without removing it.
      java.lang.Object pop()
      Pops the top item off of this stack and return it.
      java.lang.Object push​(java.lang.Object item)
      Pushes a new item onto the top of this stack.
      java.lang.Object remove()
      Removes the element on the top of the stack.
      int search​(java.lang.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.

      • Methods inherited from class java.util.ArrayList

        add, add, addAll, addAll, clear, clone, contains, ensureCapacity, equals, forEach, get, hashCode, indexOf, isEmpty, iterator, lastIndexOf, listIterator, listIterator, remove, remove, removeAll, removeIf, replaceAll, retainAll, set, size, sort, spliterator, subList, toArray, toArray, trimToSize

      • Methods inherited from class java.util.AbstractCollection

        containsAll, toString

      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.Collection

        parallelStream, removeIf, stream, toArray

      • Methods inherited from interface java.lang.Iterable

        forEach

      • Methods inherited from interface java.util.List

        containsAll

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

      • peek

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

      • pop

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

      • push

        public java.lang.Object push​(java.lang.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​(java.lang.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 java.lang.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 java.lang.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