Class BoundedFifoBuffer
java.lang.Object
java.util.AbstractCollection
org.apache.commons.collections.buffer.BoundedFifoBuffer
- All Implemented Interfaces:
Serializable
,Iterable
,Collection
,BoundedCollection
,Buffer
- Direct Known Subclasses:
CircularFifoBuffer
public class BoundedFifoBuffer
extends AbstractCollection
implements Buffer, BoundedCollection, Serializable
The BoundedFifoBuffer is a very efficient implementation of
Buffer
that is of a fixed size.
The removal order of a BoundedFifoBuffer
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()
and get()
operations
all perform in constant time. All other operations perform in linear
time or worse.
Note that this implementation is not synchronized. The following can be
used to provide synchronized access to your BoundedFifoBuffer
:
Buffer fifo = BufferUtils.synchronizedBuffer(new BoundedFifoBuffer());
This buffer prevents null objects from being added.
This class is Serializable from Commons Collections 3.1.
- Since:
- Commons Collections 3.0 (previously in main package v2.1)
- Version:
- $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
- See Also:
-
Field Summary
FieldsModifier and TypeFieldDescriptionprivate Object[]
Underlying storage arrayprivate int
Index mod maxElements of the array position following the last buffer element.private boolean
Flag to indicate if the buffer is currently full.private final int
Capacity of the bufferprivate static final long
Serialization versionprivate int
Array index of first (oldest) buffer element -
Constructor Summary
ConstructorsConstructorDescriptionConstructs a newBoundedFifoBuffer
big enough to hold 32 elements.BoundedFifoBuffer
(int size) Constructs a newBoundedFifoBuffer
big enough to hold the specified number of elements.BoundedFifoBuffer
(Collection coll) Constructs a newBoundedFifoBuffer
big enough to hold all of the elements in the specified collection. -
Method Summary
Modifier and TypeMethodDescriptionboolean
Adds the given element to this buffer.void
clear()
Clears this buffer.private int
decrement
(int index) Decrements the internal index.get()
Returns the least recently inserted element in this buffer.private int
increment
(int index) Increments the internal index.boolean
isEmpty()
Returns true if this buffer is empty; false otherwise.boolean
isFull()
Returns true if this collection is full and no new elements can be added.iterator()
Returns an iterator over this buffer's elements.int
maxSize()
Gets the maximum size of the collection (the bound).private void
Read the buffer in using a custom routine.remove()
Removes the least recently inserted element from this buffer.int
size()
Returns the number of elements stored in the buffer.private void
Write the buffer out using a custom routine.Methods inherited from class java.util.AbstractCollection
addAll, contains, containsAll, remove, removeAll, retainAll, toArray, toArray, toString
Methods inherited from class java.lang.Object
clone, equals, finalize, 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, toArray
-
Field Details
-
serialVersionUID
private static final long serialVersionUIDSerialization version- See Also:
-
elements
Underlying storage array -
start
private transient int startArray index of first (oldest) buffer element -
end
private transient int endIndex mod maxElements of the array position following the last buffer element. Buffer 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 buffer [a,b,c]. -
full
private transient boolean fullFlag to indicate if the buffer is currently full. -
maxElements
private final int maxElementsCapacity of the buffer
-
-
Constructor Details
-
BoundedFifoBuffer
public BoundedFifoBuffer()Constructs a newBoundedFifoBuffer
big enough to hold 32 elements. -
BoundedFifoBuffer
public BoundedFifoBuffer(int size) Constructs a newBoundedFifoBuffer
big enough to hold the specified number of elements.- Parameters:
size
- the maximum number of elements for this fifo- Throws:
IllegalArgumentException
- if the size is less than 1
-
BoundedFifoBuffer
Constructs a newBoundedFifoBuffer
big enough to hold all of the elements in the specified collection. That collection's elements will also be added to the buffer.- Parameters:
coll
- the collection whose elements to add, may not be null- Throws:
NullPointerException
- if the collection is null
-
-
Method Details
-
writeObject
Write the buffer out using a custom routine.- Parameters:
out
- the output stream- Throws:
IOException
-
readObject
Read the buffer in using a custom routine.- Parameters:
in
- the input stream- Throws:
IOException
ClassNotFoundException
-
size
public int size()Returns the number of elements stored in the buffer.- Specified by:
size
in interfaceCollection
- Specified by:
size
in classAbstractCollection
- Returns:
- this buffer's size
-
isEmpty
public boolean isEmpty()Returns true if this buffer is empty; false otherwise.- Specified by:
isEmpty
in interfaceCollection
- Overrides:
isEmpty
in classAbstractCollection
- Returns:
- true if this buffer is empty
-
isFull
public boolean isFull()Returns true if this collection is full and no new elements can be added.- Specified by:
isFull
in interfaceBoundedCollection
- Returns:
true
if the collection is full
-
maxSize
public int maxSize()Gets the maximum size of the collection (the bound).- Specified by:
maxSize
in interfaceBoundedCollection
- Returns:
- the maximum number of elements the collection can hold
-
clear
public void clear()Clears this buffer.- Specified by:
clear
in interfaceCollection
- Overrides:
clear
in classAbstractCollection
-
add
Adds the given element to this buffer.- Specified by:
add
in interfaceCollection
- Overrides:
add
in classAbstractCollection
- Parameters:
element
- the element to add- Returns:
- true, always
- Throws:
NullPointerException
- if the given element is nullBufferOverflowException
- if this buffer is full
-
get
Returns the least recently inserted element in this buffer.- Specified by:
get
in interfaceBuffer
- Returns:
- the least recently inserted element
- Throws:
BufferUnderflowException
- if the buffer is empty
-
remove
Removes the least recently inserted element from this buffer.- Specified by:
remove
in interfaceBuffer
- Returns:
- the least recently inserted element
- Throws:
BufferUnderflowException
- if the buffer is empty
-
increment
private int increment(int index) Increments the internal index.- Parameters:
index
- the index to increment- Returns:
- the updated index
-
decrement
private int decrement(int index) Decrements the internal index.- Parameters:
index
- the index to decrement- Returns:
- the updated index
-
iterator
Returns an iterator over this buffer's elements.- Specified by:
iterator
in interfaceCollection
- Specified by:
iterator
in interfaceIterable
- Specified by:
iterator
in classAbstractCollection
- Returns:
- an iterator over this buffer's elements
-