cpsc331.collections

Class ListStack<E>

java.lang.Object

cpsc331.collections.ListStack<E>

All Implemented Interfaces:

Stack<E>

public class ListStack<E>
extends java.lang.Object
implements Stack<E>

Provides an implementation of a Stack using a singly linked list:

All operations require constant time in the worst case.

Constructor Summary

Constructors

Constructor and Description
ListStack() Creates a linked list representing an empty stack.

Method Summary

Modifier and Type	Method and Description
boolean	isEmpty() Reports whether the stack is currently empty without changing it.
E	peek() Reports the top element of the stack without changing it.
E	pop() Removes an element from the top of the stack and reports it.
void	push(E x) Pushes a new entry onto the stack.

Methods inherited from class java.lang.Object

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

Constructor Detail

ListStack

public ListStack()

Creates a linked list representing an empty stack.

Method Detail

push

public void push(E x)

Description copied from interface: Stack

Pushes a new entry onto the stack.

Specified by:

push in interface Stack<E>

Parameters:

x - the object to be pushed onto the stack

Precondition:

1. The Stack Invariant is satisfied.
2. An element x of type E has been given as input.

Postcondition:

1. The Stack Invariant is satisfied.
2. The input object x has been pushed onto the top of the stack (which is otherwise unchanged).

peek

public E peek()

Description copied from interface: Stack

Reports the top element of the stack without changing it.

Specified by:

peek in interface Stack<E>

Returns:

the element at the top of the stack

pop

public E pop()

Description copied from interface: Stack

Removes an element from the top of the stack and reports it.

Specified by:

pop in interface Stack<E>

Returns:

the element removed from the stack

isEmpty

public boolean isEmpty()

Description copied from interface: Stack

Reports whether the stack is currently empty without changing it.

Specified by:

isEmpty in interface Stack<E>

Returns:

true if the stack is empty, and false otherwise

Precondition:

1. The Stack Invariant is satisfied.

Postcondition:

1. The Stack Invariant is satisfied.
2. The stack is not changed.
3. If the stack was empty before this operation then “true” is returned as output.
4. If the stack was not empty before this operation then “false” is returned as output.