cpsc331.collections

Class ListQueue<E>

java.lang.Object

cpsc331.collections.ListQueue<E>

All Implemented Interfaces:

Queue<E>

public class ListQueue<E>
extends java.lang.Object
implements Queue<E>

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

All operations require constant time in the worst case.

Constructor Summary

Constructors

Constructor and Description
ListQueue() Creates a linked list representing an empty queue.

Method Summary

Modifier and Type	Method and Description
void	insert(E x) Inserts a new object onto the queue.
boolean	isEmpty() Reports whether the queue is currently empty without changing it.
E	peek() Reports the front element of the queue without changing it.
E	remove() Removes an element from the front of the stack and reports it.

Methods inherited from class java.lang.Object

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

Constructor Detail

ListQueue

public ListQueue()

Creates a linked list representing an empty queue.

Method Detail

insert

public void insert(E x)

Description copied from interface: Queue

Inserts a new object onto the queue.

Specified by:

insert in interface Queue<E>

Parameters:

x - the object to be pushed onto the queue

Precondition:

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

Postcondition:

1. The Queue Invariant is satisfied.
2. The input object x has been inserted at the rear of the queue (which is otherwise unchanged).

peek

public E peek()

Description copied from interface: Queue

Reports the front element of the queue without changing it.

Specified by:

peek in interface Queue<E>

Returns:

the element at the front of the queue

remove

public E remove()

Description copied from interface: Queue

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

Specified by:

remove in interface Queue<E>

Returns:

the element removed from the queue

isEmpty

public boolean isEmpty()

Description copied from interface: Queue

Reports whether the queue is currently empty without changing it.

Specified by:

isEmpty in interface Queue<E>

Returns:

true if the queue is empty, and false otherwise

Precondition:

1. The Queue Invariant is satisfied.

Postcondition:

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