Queue (Algorithms 4/e)

Object
- edu.princeton.cs.algs4.Queue<Item>

Type Parameters:

Item - the generic type of an item in this queue

All Implemented Interfaces:

Iterable<Item>
```
public class Queue<Item>
extends Object
implements 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. See ResizingArrayQueue for a version that uses a resizing array. 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.

Author:

Robert Sedgewick, Kevin Wayne

Constructor Summary

Constructors
Constructor and Description

Queue()
Initializes an empty queue.

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

Method Summary

All Methods Static Methods Instance Methods Concrete 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 the item to this queue.
`boolean`	`isEmpty()` Returns true if this queue is empty.
`Iterator<Item>`	`iterator()` Returns an iterator that iterates over the items in this queue in FIFO order.
`static void`	`main(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.
`String`	`toString()` Returns a string representation of this queue.

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

Methods inherited from interface Iterable
forEach, spliterator

- Constructor Detail
  - Queue
```
public Queue()
```
    Initializes an empty queue.
- Method Detail
  - isEmpty
```
public boolean isEmpty()
```
    Returns true if this queue is empty.
    
    Returns:
    
    true if this queue is empty; false otherwise
  - size
```
public int size()
```
    Returns the number of items in this queue.
    
    Returns:
    
    the number of items in this queue
  - peek
```
public Item peek()
```
    Returns the item least recently added to this queue.
    
    Returns:
    
    the item least recently added to this queue
    
    Throws:
    
    NoSuchElementException - if this queue is empty
  - enqueue
```
public void enqueue(Item item)
```
    Adds the item to this queue.
    
    Parameters:
    
    item - the item to add
  - 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:
    
    NoSuchElementException - if this queue is empty
  - toString
```
public String toString()
```
    Returns a string representation of this queue.
    
    Overrides:
    
    toString in class Object
    
    Returns:
    
    the sequence of items in FIFO order, separated by spaces
  - iterator
```
public Iterator<Item> iterator()
```
    Returns an iterator that iterates over the items in this queue in FIFO order.
    
    Specified by:
    
    iterator in interface Iterable<Item>
    
    Returns:
    
    an iterator that iterates over the items in this queue in FIFO order
  - main
```
public static void main(String[] args)
```
    Unit tests the Queue data type.
    
    Parameters:
    
    args - the command-line arguments

Class Queue<Item>

Constructor Summary

Method Summary

Methods inherited from class Object

Methods inherited from interface Iterable

Constructor Detail

Queue

Method Detail

isEmpty

size

peek

enqueue

dequeue

toString

iterator

main