edu.princeton.cs.algorithms

Class LinkedStack<Item>

java.lang.Object

edu.princeton.cs.algorithms.LinkedStack<Item>

All Implemented Interfaces:

Iterable<Item>

public class LinkedStack<Item>
extends Object
implements Iterable<Item>

The LinkedStack class represents a last-in-first-out (LIFO) stack of generic items. It supports the usual push and pop operations, along with methods for peeking at the top item, testing if the stack is empty, and iterating through the items in LIFO order.

This implementation uses a singly-linked list with a non-static nested class for linked-list nodes. See Stack for a version that uses a static nested class. The push, pop, peek, size, and is-empty operations all take constant time in the worst case.

For additional documentation, see Section 1.3 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

Author:

Robert Sedgewick, Kevin Wayne

Constructor Summary

Constructors

Constructor and Description
LinkedStack() Initializes an empty stack.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	isEmpty() Is this stack empty?
Iterator<Item>	iterator() Returns an iterator to this stack that iterates through the items in LIFO order.
static void	main(String[] args) Unit tests the LinkedStack data type.
Item	peek() Returns (but does not remove) the item most recently added to this stack.
Item	pop() Removes and returns the item most recently added to this stack.
void	push(Item item) Adds the item to this stack.
int	size() Returns the number of items in the stack.
String	toString() Returns a string representation of this stack.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

LinkedStack

public LinkedStack()

Initializes an empty stack.

Method Detail

isEmpty

public boolean isEmpty()

Is this stack empty?

Returns:

true if this stack is empty; false otherwise

size

public int size()

Returns the number of items in the stack.

Returns:

the number of items in the stack

push

public void push(Item item)

Adds the item to this stack.

Parameters:

item - the item to add

pop

public Item pop()

Removes and returns the item most recently added to this stack.

Returns:

the item most recently added

Throws:

NoSuchElementException - if this stack is empty

peek

public Item peek()

Returns (but does not remove) the item most recently added to this stack.

Returns:

the item most recently added to this stack

Throws:

NoSuchElementException - if this stack is empty

toString

public String toString()

Returns a string representation of this stack.

Overrides:

toString in class Object

Returns:

the sequence of items in the stack in LIFO order, separated by spaces

iterator

public Iterator<Item> iterator()

Returns an iterator to this stack that iterates through the items in LIFO order.

Specified by:

iterator in interface Iterable<Item>

Returns:

an iterator to this stack that iterates through the items in LIFO order.

main

public static void main(String[] args)

Unit tests the LinkedStack data type.