Apache Commons Collections 4.4 · org.apache.commons.collections4.queue.CircularFifoQueue

Field Summary

Modifier and Type	Field and Description
private transient E[]	elements Underlying storage array.
private transient int	end Index mod maxElements of the array position following the last queue element.
private transient boolean	full Flag to indicate if the queue is currently full.
private final int	maxElements Capacity of the queue.
private static final long	serialVersionUID Serialization version.
private transient int	start Array index of first (oldest) queue element.

Constructor Summary

Access	Constructor and Description
public	CircularFifoQueue() Constructor that creates a queue with the default size of 32.
public	CircularFifoQueue(final int the size of the queue (cannot be changed) size) Constructor that creates a queue with the specified size.
public	CircularFifoQueue(final Collection<? extends E> the collection to copy into the queue, may not be null coll) Constructor that creates a queue from the specified collection.

Method Summary

Modifier and Type	Method and Description
public boolean	Returns: true, always add(final E the element to add element) Overrides java.util.AbstractCollection.add. Implements java.util.Queue.add, java.util.Collection.add. Adds the given element to this queue.
public void	clear() Overrides java.util.AbstractCollection.clear. Implements java.util.Collection.clear. Clears this queue.
private int	Returns: the updated index decrement(int the index to decrement index) Decrements the internal index.
public E	element() Implements java.util.Queue.element. Retrieves, but does not remove, the head of this queue.
public E	Returns: the element at position `index` get(final int the position of the element in the queue index) Returns the element at the specified position in this queue.
private int	Returns: the updated index increment(int the index to increment index) Increments the internal index.
public boolean	Returns: `true` if the capacity limit has been reached, `false` otherwise 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.
public boolean	Returns: true if this queue is empty isEmpty() Overrides java.util.AbstractCollection.isEmpty. Implements java.util.Collection.isEmpty. Returns true if this queue is empty; false otherwise.
public boolean	Returns: always returns `false` isFull() Implements org.apache.commons.collections4.BoundedCollection.isFull. Returns true if this collection is full and no new elements can be added.
public Iterator<E>	Returns: an iterator over this queue's elements iterator() Implements abstract java.util.AbstractCollection.iterator. Implements java.util.Collection.iterator. Returns an iterator over this queue's elements.
public int	Returns: the maximum number of elements the collection can hold maxSize() Implements org.apache.commons.collections4.BoundedCollection.maxSize. Gets the maximum size of the collection (the bound).
public boolean	Returns: true, always offer(final E the element to add element) Implements java.util.Queue.offer. Adds the given element to this queue.
public E	peek() Implements java.util.Queue.peek. Retrieves, but does not remove, the head of this queue, or returns `null` if this queue is empty.
public E	poll() Implements java.util.Queue.poll. Retrieves and removes the head of this queue, or returns `null` if this queue is empty.
private void	readObject(final ObjectInputStream the input stream in) Read the queue in using a custom routine.
public E	remove() Implements java.util.Queue.remove. Retrieves and removes the head of this queue.
public int	Returns: this queue's size size() Implements abstract java.util.AbstractCollection.size. Implements java.util.Collection.size. Returns the number of elements stored in the queue.
private void	writeObject(final ObjectOutputStream the output stream out) Write the queue out using a custom routine.

Inherited from java.util.AbstractCollection:: addAll contains containsAll remove removeAll retainAll toArray toArray toString

Field Detail

elements	back to summary
private transient E[] elements Underlying storage array.

end	back to summary
private transient int end Index mod maxElements of the array position following the last queue element. Queue elements start at elements[start] and "wrap around" elements[maxElements-1], ending at elements[decrement(end)]. For example, elements = {c,a,b}, start=1, end=1 corresponds to the queue [a,b,c].

full	back to summary
private transient boolean full Flag to indicate if the queue is currently full.

maxElements	back to summary
private final int maxElements Capacity of the queue.

serialVersionUID	back to summary
private static final long serialVersionUID Serialization version.

start	back to summary
private transient int start Array index of first (oldest) queue element.

Constructor Detail

CircularFifoQueue	back to summary
public CircularFifoQueue() Constructor that creates a queue with the default size of 32.

CircularFifoQueue	back to summary
public CircularFifoQueue(final int size) Constructor that creates a queue with the specified size. Parameters size:int the size of the queue (cannot be changed) Annotations @SuppressWarnings:unchecked Exceptions IllegalArgumentException: if the size is < 1

CircularFifoQueue

back to summary

public CircularFifoQueue(final int size)

Constructor that creates a queue with the specified size.

Parameters

size:int: the size of the queue (cannot be changed)

Annotations

@SuppressWarnings:unchecked

Exceptions

IllegalArgumentException:: if the size is < 1

CircularFifoQueue	back to summary
public CircularFifoQueue(final Collection<? extends E> coll) Constructor that creates a queue from the specified collection. The collection size also sets the queue size. Parameters coll:Collection<? extends E> the collection to copy into the queue, may not be null Exceptions NullPointerException: if the collection is null

CircularFifoQueue

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public CircularFifoQueue(final Collection<? extends E> coll)

Constructor that creates a queue from the specified collection. The collection size also sets the queue size.

Parameters

coll:Collection<? extends E>: the collection to copy into the queue, may not be null

Exceptions

NullPointerException:: if the collection is null

Method Detail

add	back to summary
public boolean add(final E element) Overrides java.util.AbstractCollection.add. Implements java.util.Queue.add, java.util.Collection.add. 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. Parameters element:E the element to add Returns:boolean true, always Annotations @Override Exceptions NullPointerException: if the given element is null

add

back to summary

public boolean add(final E element)

Overrides java.util.AbstractCollection.add.

Implements java.util.Queue.add, java.util.Collection.add.

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.

Parameters

element:E: the element to add

Returns:boolean

true, always

Annotations

@Override

Exceptions

NullPointerException:: if the given element is null

clear	back to summary
public void clear() Overrides java.util.AbstractCollection.clear. Implements java.util.Collection.clear. Clears this queue. Annotations @Override

clear

back to summary

public void clear()

Overrides java.util.AbstractCollection.clear.

Implements java.util.Collection.clear.

Clears this queue.

Annotations

@Override

decrement	back to summary
private int decrement(int index) Decrements the internal index. Parameters index:int the index to decrement Returns:int the updated index

decrement

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private int decrement(int index)

Decrements the internal index.

Parameters

index:int: the index to decrement

Returns:int

the updated index

element back to summary

element	back to summary
public E element() Implements java.util.Queue.element. Doc from java.util.Queue.element. Retrieves, but does not remove, the head of this queue. This method differs from `peek` only in that it throws an exception if this queue is empty. Returns:E the head of this queue Annotations @Override

public E element()

Implements java.util.Queue.element.

Doc from java.util.Queue.element.

Retrieves, but does not remove, the head of this queue. This method differs from peek only in that it throws an exception if this queue is empty.

Returns:E

the head of this queue

Annotations

@Override

get back to summary

get	back to summary
public E get(final int index) Returns the element at the specified position in this queue. Parameters index:int the position of the element in the queue Returns:E the element at position `index` Exceptions NoSuchElementException: if the requested position is outside the range [0, size)

public E get(final int index)

Returns the element at the specified position in this queue.

Parameters

index:int: the position of the element in the queue

Returns:E

the element at position index

Exceptions

NoSuchElementException:: if the requested position is outside the range [0, size)

increment	back to summary
private int increment(int index) Increments the internal index. Parameters index:int the index to increment Returns:int the updated index

increment

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private int increment(int index)

Increments the internal index.

Parameters

index:int: the index to increment

Returns:int

the updated index

isAtFullCapacity back to summary

isAtFullCapacity	back to summary
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:boolean `true` if the capacity limit has been reached, `false` otherwise Since 4.1

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:boolean: true if the capacity limit has been reached, false otherwise
Since: 4.1

isEmpty	back to summary
public boolean isEmpty() Overrides java.util.AbstractCollection.isEmpty. Implements java.util.Collection.isEmpty. Returns true if this queue is empty; false otherwise. Returns:boolean true if this queue is empty Annotations @Override

isEmpty

back to summary

public boolean isEmpty()

Overrides java.util.AbstractCollection.isEmpty.

Implements java.util.Collection.isEmpty.

Returns true if this queue is empty; false otherwise.

Returns:boolean

true if this queue is empty

Annotations

@Override

isFull back to summary

isFull	back to summary
public boolean isFull() Implements org.apache.commons.collections4.BoundedCollection.isFull. Doc from org.apache.commons.collections4.BoundedCollection.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`. Returns:boolean always returns `false` Annotations @Override

public boolean isFull()

Implements org.apache.commons.collections4.BoundedCollection.isFull.

Doc from org.apache.commons.collections4.BoundedCollection.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.

Returns:boolean

always returns false

Annotations

@Override

iterator	back to summary
public Iterator<E> iterator() Implements abstract java.util.AbstractCollection.iterator. Implements java.util.Collection.iterator. Returns an iterator over this queue's elements. Returns:Iterator<E> an iterator over this queue's elements Annotations @Override

iterator

back to summary

public Iterator<E> iterator()

Implements abstract java.util.AbstractCollection.iterator.

Implements java.util.Collection.iterator.

Returns an iterator over this queue's elements.

Returns:Iterator<E>

an iterator over this queue's elements

Annotations

@Override

maxSize	back to summary
public int maxSize() Implements org.apache.commons.collections4.BoundedCollection.maxSize. Gets the maximum size of the collection (the bound). Returns:int the maximum number of elements the collection can hold Annotations @Override

maxSize

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public int maxSize()

Implements org.apache.commons.collections4.BoundedCollection.maxSize.

Gets the maximum size of the collection (the bound).

Returns:int

the maximum number of elements the collection can hold

Annotations

@Override

offer	back to summary
public boolean offer(final E element) Implements java.util.Queue.offer. 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. Parameters element:E the element to add Returns:boolean true, always Annotations @Override Exceptions NullPointerException: if the given element is null

offer

back to summary

public boolean offer(final E element)

Implements java.util.Queue.offer.

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.

Parameters

element:E: the element to add

Returns:boolean

true, always

Annotations

@Override

Exceptions

NullPointerException:: if the given element is null

peek back to summary

peek	back to summary
public E peek() Implements java.util.Queue.peek. Doc from java.util.Queue.peek. Retrieves, but does not remove, the head of this queue, or returns `null` if this queue is empty. Returns:E the head of this queue, or `null` if this queue is empty Annotations @Override

public E peek()

Implements java.util.Queue.peek.

Doc from java.util.Queue.peek.

Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.

Returns:E

the head of this queue, or null if this queue is empty

Annotations

@Override

poll back to summary

poll	back to summary
public E poll() Implements java.util.Queue.poll. Doc from java.util.Queue.poll. Retrieves and removes the head of this queue, or returns `null` if this queue is empty. Returns:E the head of this queue, or `null` if this queue is empty Annotations @Override

public E poll()

Implements java.util.Queue.poll.

Doc from java.util.Queue.poll.

Retrieves and removes the head of this queue, or returns null if this queue is empty.

Returns:E

the head of this queue, or null if this queue is empty

Annotations

@Override

readObject	back to summary
private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException Read the queue in using a custom routine. Parameters in:ObjectInputStream the input stream Annotations @SuppressWarnings:unchecked Exceptions IOException: if an I/O error occurs while writing to the output stream ClassNotFoundException: if the class of a serialized object can not be found

readObject

back to summary

private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException

Read the queue in using a custom routine.

Parameters

in:ObjectInputStream: the input stream

Annotations

@SuppressWarnings:unchecked

Exceptions

IOException:: if an I/O error occurs while writing to the output stream
ClassNotFoundException:: if the class of a serialized object can not be found

remove back to summary

remove	back to summary
public E remove() Implements java.util.Queue.remove. Doc from java.util.Queue.remove. Retrieves and removes the head of this queue. This method differs from `poll()` only in that it throws an exception if this queue is empty. Returns:E the head of this queue Annotations @Override

public E remove()

Implements java.util.Queue.remove.

Doc from java.util.Queue.remove.

Retrieves and removes the head of this queue. This method differs from poll() only in that it throws an exception if this queue is empty.

Returns:E

the head of this queue

Annotations

@Override

size	back to summary
public int size() Implements abstract java.util.AbstractCollection.size. Implements java.util.Collection.size. Returns the number of elements stored in the queue. Returns:int this queue's size Annotations @Override

size

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public int size()

Implements abstract java.util.AbstractCollection.size.

Implements java.util.Collection.size.

Returns the number of elements stored in the queue.

Returns:int

this queue's size

Annotations

@Override

writeObject	back to summary
private void writeObject(final ObjectOutputStream out) throws IOException Write the queue out using a custom routine. Parameters out:ObjectOutputStream the output stream Exceptions IOException: if an I/O error occurs while writing to the output stream

writeObject

back to summary

private void writeObject(final ObjectOutputStream out) throws IOException

Write the queue out using a custom routine.

Parameters

out:ObjectOutputStream: the output stream

Exceptions

IOException:: if an I/O error occurs while writing to the output stream

public Class CircularFifoQueue<E>

Field Summary

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Field Detail

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