xxl.collections
Interface Queue

All Known Implementing Classes:

AbstractQueue

public abstract interface Queue

extends PeekIterator

This interface adds queue-like access to an object.

Field Summary

static Function

FACTORY_METHOD A factory method to create a default Queue.

Method Summary

void	clear() Removes all elements form the Queue.
void	close() Releases resources needed to access data.
boolean	hasNext() Returns true if the iteration has more elements.
void	insert(java.lang.Object object) Appends an object to the end of the queue.
void	insertAll(java.util.Iterator objects) Appends all objects of the specified iterator to the end of the queue.
java.lang.Object	next() Returns the next element in the iteration.
java.lang.Object	peek() Shows the next element in the iteration without removing it.
java.lang.Object	replace(java.lang.Object object) Inserts a given object and returns this.next().
java.util.Iterator	replaceAll(java.util.Iterator objects) Inserts a given Iterator of objects and returns an Iterator wrapping calls to this.next().
int	size() Returns the size of the Queue.
boolean	supportsPeek() Returns true if the peek operation is supported by this PeekIterator.

Methods inherited from interface xxl.cursors.PeekIterator

remove

Field Detail

FACTORY_METHOD

public static final Function FACTORY_METHOD

A factory method to create a default Queue. Each implementation of Queue should have a field FACTORY_METHOD which is a factory method that implements three variants of invoke()

• Object invoke(): returns new Queue().
• Object invoke(Object iterator): returns new Queue(iterator).
• Object invoke(Object[] internalDataStructure): returns new Queue( () internalDataStructure[0]).

Method Detail

insert

public void insert(java.lang.Object object)

Appends an object to the end of the queue.

Parameters:

object - object to be appended to the queue

insertAll

public void insertAll(java.util.Iterator objects)

Appends all objects of the specified iterator to the end of the queue. This means that the following code should be executed:

while(objects.hasNext()){
insert(objects.next());
}

We did not include this code, because Java does not support multiple inheritance. Note, that this method is implemented in AbstractQueue. IMPORTANT: This method is not named insertAll(Iterator) for the follwing reason: consider that you have a Queue whose entries are Iterators. A call to insert would result in a call to insert(Iterator) and all the elements of the Iterator would be inserted into the Queue, which would not be what you wanted and is a very nasty bug.

Parameters:

objects - iterator of objects

hasNext

public boolean hasNext()

Returns true if the iteration has more elements.

Specified by:

hasNext in interface PeekIterator

Returns:

true if the iterator has more elements.

peek

public java.lang.Object peek()
                      throws java.util.NoSuchElementException

Shows the next element in the iteration without removing it.

Specified by:

peek in interface PeekIterator

Returns:

the next element in the iteration

Throws:

java.util.NoSuchElementException - iteration has no more elements

java.lang.UnsupportedOperationException - if the peek operation is not supported by this PeekIterator

next

public java.lang.Object next()
                      throws java.util.NoSuchElementException

Returns the next element in the iteration.

Specified by:

next in interface PeekIterator

Returns:

the next element in the iteration

Throws:

java.util.NoSuchElementException - iteration has no more elements

replace

public java.lang.Object replace(java.lang.Object object)
                         throws java.util.NoSuchElementException

Inserts a given object and returns this.next().

replaceAll

public java.util.Iterator replaceAll(java.util.Iterator objects)
                              throws java.util.NoSuchElementException

Inserts a given Iterator of objects and returns an Iterator wrapping calls to this.next(). (lazy evaluation)

size

public int size()

Returns the size of the Queue.

supportsPeek

public boolean supportsPeek()

Returns true if the peek operation is supported by this PeekIterator.

Specified by:

supportsPeek in interface PeekIterator

Returns:

true if the peek operation is supported by this PeekIterator

clear

public void clear()

Removes all elements form the Queue.

close

public void close()

Releases resources needed to access data.