java.util.Stack

Stack<E>

Java SE 6

Extends: AbstractCollection > AbstractList > Vector

The Stack class represents a last-in-first-out (LIFO) stack of objects. It extends class Vector with five operations that allow a vector to be treated as a stack. The usual push and pop operations are provided, as well as a method to peek at the top item on the stack, a method to test for whether the stack is empty, and a method to search the stack for an item and discover how far it is from the top.

When a stack is first created, it contains no items.

A more complete and consistent set of LIFO stack operations is provided by the Deque interface and its implementations, which should be used in preference to this class. For example:

   Deque<Integer> stack = new ArrayDeque<Integer>();

version	1.30, 11/17/05
since	JDK1.0

Constructors

public

Stack()
Creates an empty Stack.

Methods

public boolean

empty() Details

Tests if this stack is empty.

return true if and only if this stack contains no items; false otherwise.

public Object

peek() Details

Looks at the object at the top of this stack without removing it from the stack.

return	the object at the top of this stack (the last item of the `Vector` object).
Throws	EmptyStackException: if this stack is empty.

public Object

pop() Details

Removes the object at the top of this stack and returns that object as the value of this function.

return	The object at the top of this stack (the last item of the `Vector` object).
Throws	EmptyStackException: if this stack is empty.

public Object

push(Object item) Details

Pushes an item onto the top of this stack. This has exactly the same effect as:

 addElement(item)

item	the item to be pushed onto this stack.
return	the `item` argument.
See also	addElement

public int

search(Object o) Details

Returns the 1-based position where an object is on this stack. If the object o occurs as an item in this stack, this method returns the distance from the top of the stack of the occurrence nearest the top of the stack; the topmost item on the stack is considered to be at distance 1. The equals method is used to compare o to the items in this stack.

o	the desired object.
return	the 1-based position from the top of the stack where the object is located; the return value `-1` indicates that the object is not on the stack.

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Java SE 6