CircularFifoQueue ("The Adobe AEM Quickstart and Web Application.")

java.lang.Object
- java.util.AbstractCollection<E>
- - org.apache.commons.collections4.queue.CircularFifoQueue<E>

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable<E>, java.util.Collection<E>, java.util.Queue<E>, BoundedCollection<E>
```
public class CircularFifoQueue<E>
extends java.util.AbstractCollection<E>
implements java.util.Queue<E>, BoundedCollection<E>, java.io.Serializable
```
CircularFifoQueue is a first-in first-out queue with a fixed size that replaces its oldest element if full.
The removal order of a CircularFifoQueue is based on the insertion order; elements are removed in the same order in which they were added. The iteration order is the same as the removal order.
The add(Object), remove(), peek(), poll(), offer(Object) operations all perform in constant time. All other operations perform in linear time or worse.
This queue prevents null objects from being added.

Since:

4.0

See Also:

Serialized Form

Constructor Summary

Constructors
Constructor and Description
`CircularFifoQueue()` Constructor that creates a queue with the default size of 32.
`CircularFifoQueue(java.util.Collection<? extends E> coll)` Constructor that creates a queue from the specified collection.
`CircularFifoQueue(int size)` Constructor that creates a queue with the specified size.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`add(E element)` Adds the given element to this queue.
`void`	`clear()` Clears this queue.
`E`	`element()`
`E`	`get(int index)` Returns the element at the specified position in this queue.
`boolean`	`isAtFullCapacity()` Returns `true` if the capacity limit of this queue has been reached, i.e.
`boolean`	`isEmpty()` Returns true if this queue is empty; false otherwise.
`boolean`	`isFull()` Returns true if this collection is full and no new elements can be added.
`java.util.Iterator<E>`	`iterator()` Returns an iterator over this queue's elements.
`int`	`maxSize()` Gets the maximum size of the collection (the bound).
`boolean`	`offer(E element)` Adds the given element to this queue.
`E`	`peek()`
`E`	`poll()`
`E`	`remove()`
`int`	`size()` Returns the number of elements stored in the queue.

Methods inherited from class java.util.AbstractCollection
addAll, contains, containsAll, remove, removeAll, retainAll, toArray, toArray, toString

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

Methods inherited from interface java.util.Collection
addAll, contains, containsAll, equals, hashCode, parallelStream, remove, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray

Methods inherited from interface java.lang.Iterable
forEach

- Constructor Detail
  - CircularFifoQueue
```
public CircularFifoQueue()
```
    Constructor that creates a queue with the default size of 32.
  - CircularFifoQueue
```
public CircularFifoQueue(int size)
```
    Constructor that creates a queue with the specified size.
    
    Parameters:
    
    size - the size of the queue (cannot be changed)
    
    Throws:
    
    java.lang.IllegalArgumentException - if the size is < 1
  - CircularFifoQueue
```
public CircularFifoQueue(java.util.Collection<? extends E> coll)
```
    Constructor that creates a queue from the specified collection. The collection size also sets the queue size.
    
    Parameters:
    
    coll - the collection to copy into the queue, may not be null
    
    Throws:
    
    java.lang.NullPointerException - if the collection is null
- Method Detail
  - size
```
public int size()
```
    Returns the number of elements stored in the queue.
    
    Specified by:
    
    size in interface java.util.Collection<E>
    
    Specified by:
    
    size in class java.util.AbstractCollection<E>
    
    Returns:
    
    this queue's size
  - isEmpty
```
public boolean isEmpty()
```
    Returns true if this queue is empty; false otherwise.
    
    Specified by:
    
    isEmpty in interface java.util.Collection<E>
    
    Overrides:
    
    isEmpty in class java.util.AbstractCollection<E>
    
    Returns:
    
    true if this queue is empty
  - isFull
```
public boolean isFull()
```
    Returns true if this collection is full and no new elements can be added.
    A CircularFifoQueue can never be full, thus this returns always false.
    
    Specified by:
    
    isFull in interface BoundedCollection<E>
    
    Returns:
    
    always returns false
  - isAtFullCapacity
```
public boolean isAtFullCapacity()
```
    Returns true if the capacity limit of this queue has been reached, i.e. the number of elements stored in the queue equals its maximum size.
    
    Returns:
    
    true if the capacity limit has been reached, false otherwise
    
    Since:
    
    4.1
  - maxSize
```
public int maxSize()
```
    Gets the maximum size of the collection (the bound).
    
    Specified by:
    
    maxSize in interface BoundedCollection<E>
    
    Returns:
    
    the maximum number of elements the collection can hold
  - clear
```
public void clear()
```
    Clears this queue.
    
    Specified by:
    
    clear in interface java.util.Collection<E>
    
    Overrides:
    
    clear in class java.util.AbstractCollection<E>
  - add
```
public boolean add(E element)
```
    Adds the given element to this queue. If the queue is full, the least recently added element is discarded so that a new element can be inserted.
    
    Specified by:
    
    add in interface java.util.Collection<E>
    
    Specified by:
    
    add in interface java.util.Queue<E>
    
    Overrides:
    
    add in class java.util.AbstractCollection<E>
    
    Parameters:
    
    element - the element to add
    
    Returns:
    
    true, always
    
    Throws:
    
    java.lang.NullPointerException - if the given element is null
  - get
```
public E get(int index)
```
    Returns the element at the specified position in this queue.
    
    Parameters:
    
    index - the position of the element in the queue
    
    Returns:
    
    the element at position index
    
    Throws:
    
    java.util.NoSuchElementException - if the requested position is outside the range [0, size)
  - offer
```
public boolean offer(E element)
```
    Adds the given element to this queue. If the queue is full, the least recently added element is discarded so that a new element can be inserted.
    
    Specified by:
    
    offer in interface java.util.Queue<E>
    
    Parameters:
    
    element - the element to add
    
    Returns:
    
    true, always
    
    Throws:
    
    java.lang.NullPointerException - if the given element is null
  - poll
```
public E poll()
```
    Specified by:
    
    poll in interface java.util.Queue<E>
  - element
```
public E element()
```
    Specified by:
    
    element in interface java.util.Queue<E>
  - peek
```
public E peek()
```
    Specified by:
    
    peek in interface java.util.Queue<E>
  - remove
```
public E remove()
```
    Specified by:
    
    remove in interface java.util.Queue<E>
  - iterator
```
public java.util.Iterator<E> iterator()
```
    Returns an iterator over this queue's elements.
    
    Specified by:
    
    iterator in interface java.lang.Iterable<E>
    
    Specified by:
    
    iterator in interface java.util.Collection<E>
    
    Specified by:
    
    iterator in class java.util.AbstractCollection<E>
    
    Returns:
    
    an iterator over this queue's elements

Class CircularFifoQueue<E>

Constructor Summary

Method Summary

Methods inherited from class java.util.AbstractCollection

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Collection

Methods inherited from interface java.lang.Iterable

Constructor Detail

CircularFifoQueue

CircularFifoQueue

CircularFifoQueue

Method Detail

size

isEmpty

isFull

isAtFullCapacity

maxSize

clear

add

get

offer

poll

element

peek

remove

iterator