Queue

java.lang.Object
- Queue<Item>

All Implemented Interfaces:

java.lang.Iterable<Item>
```
public class Queue<Item>
extends java.lang.Object
implements java.lang.Iterable<Item>
```
The Queue class represents a first-in-first-out (FIFO) queue of generic items. It supports the usual enqueue and dequeue operations, along with methods for peeking at the first item, testing if the queue is empty, and iterating through the items in FIFO order.
This implementation uses a singly-linked list with a static nested class for linked-list nodes. See LinkedQueue for the version from the textbook that uses a non-static nested class. The enqueue, dequeue, 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.

Constructor Summary

Constructors
Constructor and Description

Queue()
Constructor: initializes an empty queue.

Constructors
Constructor and Description
`Queue()` Constructor: initializes an empty queue.

Method Summary

Methods
Modifier and Type	Method and Description
`Item`	`dequeue()` Removes and returns the item on this queue that was least recently added.
`void`	`enqueue(Item item)` Adds item to this queue.
`boolean`	`isEmpty()` Is this queue empty?
`java.util.Iterator<Item>`	`iterator()` Returns an iterator that iterates over the items in this queue in FIFO order.
`static void`	`main(java.lang.String[] args)` Unit tests the `Queue` data type.
`Item`	`peek()` Returns the item least recently added to this queue.
`int`	`size()` Returns the number of items in this queue.
`java.lang.String`	`toString()` Returns a string representation of this queue.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - Queue
```
public Queue()
```
    Constructor: initializes an empty queue.
- Method Detail
  - isEmpty
```
public boolean isEmpty()
```
    Is this queue empty?
  - size
```
public int size()
```
    Returns the number of items in this queue.
  - peek
```
public Item peek()
```
    Returns the item least recently added to this queue.
    
    Throws:
    
    java.util.NoSuchElementException - if this queue is empty
  - enqueue
```
public void enqueue(Item item)
```
    Adds item to this queue.
  - dequeue
```
public Item dequeue()
```
    Removes and returns the item on this queue that was least recently added.
    
    Returns:
    the item on this queue that was least recently added
    
    Throws:
    
    java.util.NoSuchElementException - if this queue is empty
  - toString
```
public java.lang.String toString()
```
    Returns a string representation of this queue.
    
    Overrides:
    
    toString in class java.lang.Object
    
    Returns:
    the sequence of items in FIFO order, separated by spaces
  - iterator
```
public java.util.Iterator<Item> iterator()
```
    Returns an iterator that iterates over the items in this queue in FIFO order.
    
    Specified by:
    
    iterator in interface java.lang.Iterable<Item>
    
    Returns:
    an iterator that iterates over the items in this queue in FIFO order
  - main
```
public static void main(java.lang.String[] args)
```
    Unit tests the Queue data type.

Class Queue<Item>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Queue

Method Detail

isEmpty

size

peek

enqueue

dequeue

toString

iterator

main