SynchronizedHardReferenceQueue (Blazegraph Database Platform 2.1.5 API)

java.lang.Object
- com.bigdata.cache.SynchronizedHardReferenceQueue<T>

All Implemented Interfaces:

IHardReferenceQueue<T>
```
public class SynchronizedHardReferenceQueue<T>
extends Object
implements IHardReferenceQueue<T>
```
Thread-safe version.

Version:

$Id$

Author:

Bryan Thompson

Field Summary

Fields
Modifier and Type Field and Description

protected HardReferenceQueue<T> queue
Note: Synchronization for the inner queue is realized using the outer reference!
- Fields inherited from interface com.bigdata.cache.IHardReferenceQueue
  DEFAULT_NSCAN

Fields
Modifier and Type	Field and Description
`protected HardReferenceQueue<T>`	`queue` Note: Synchronization for the inner `queue` is realized using the outer reference!

Constructor Summary

Constructors
Constructor and Description
`SynchronizedHardReferenceQueue(HardReferenceQueueEvictionListener<T> listener, int capacity)` Defaults the #of references to scan on append requests to 10.
`SynchronizedHardReferenceQueue(HardReferenceQueueEvictionListener<T> listener, int capacity, int nscan)` Core impl.

Method Summary

Methods
Modifier and Type	Method and Description
`boolean`	`add(T ref)` Add a reference to the cache.
`protected void`	`beforeOffer(T t)` All attempts to add an element to the buffer invoke this hook before checking the remaining capacity in the buffer.
`int`	`capacity()` The cache capacity.
`void`	`clear(boolean clearRefs)` Clears the cache (sets the head, tail and count to zero) without generating eviction notices.
`boolean`	`evict()` Evict the LRU reference.
`void`	`evictAll(boolean clearRefs)` Evict all references, starting with the LRU reference and proceeding to the MRU reference.
`HardReferenceQueueEvictionListener<T>`	`getListener()`
`boolean`	`isEmpty()` True iff the cache is empty.
`boolean`	`isFull()` True iff the cache is full.
`int`	`nscan()` The #of references that are tested on append requests.
`T`	`peek()` The reference at the tail of the queue.
`boolean`	`scanHead(int nscan, T ref)`
`boolean`	`scanTail(int nscan, T ref)`
`int`	`size()` The #of references in the cache.

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

- Field Detail
  - queue
```
protected final HardReferenceQueue<T> queue
```
    Note: Synchronization for the inner queue is realized using the outer reference!
- Constructor Detail
  - SynchronizedHardReferenceQueue
```
public SynchronizedHardReferenceQueue(HardReferenceQueueEvictionListener<T> listener,
                              int capacity)
```
    Defaults the #of references to scan on append requests to 10.
    
    Parameters:
    listener - The listener on which cache evictions are reported.
    capacity - The maximum #of references that can be stored on the cache. There is no guarantee that all stored references are distinct.
  - SynchronizedHardReferenceQueue
```
public SynchronizedHardReferenceQueue(HardReferenceQueueEvictionListener<T> listener,
                              int capacity,
                              int nscan)
```
    Core impl.
    
    Parameters:
    listener - The listener on which cache evictions are reported (optional).
    capacity - The maximum #of references that can be stored on the cache. There is no guarantee that all stored references are distinct.
    nscan - The #of references to scan from the MRU position before appended a reference to the cache. Scanning is used to reduce the chance that references that are touched several times in near succession from entering the cache more than once. The #of reference tests trades off against the latency of adding a reference to the cache.
- Method Detail
  - beforeOffer
```
protected void beforeOffer(T t)
```
    All attempts to add an element to the buffer invoke this hook before checking the remaining capacity in the buffer. The caller will be synchronized on this when this method is invoked.
  - capacity
```
public final int capacity()
```
    Description copied from interface: IHardReferenceQueue
    
    The cache capacity.
    
    Specified by:
    
    capacity in interface IHardReferenceQueue<T>
  - getListener
```
public HardReferenceQueueEvictionListener<T> getListener()
```
  - nscan
```
public int nscan()
```
    Description copied from interface: IHardReferenceQueue
    
    The #of references that are tested on append requests.
    
    Specified by:
    
    nscan in interface IHardReferenceQueue<T>
  - add
```
public boolean add(T ref)
```
    Description copied from interface: IHardReferenceQueue
    
    Add a reference to the cache. If the reference was recently added to the cache then this is a NOP. Otherwise the reference is appended to the cache. If a reference is appended to the cache and then cache is at capacity, then the LRU reference is first evicted from the cache.
    
    Specified by:
    
    add in interface IHardReferenceQueue<T>
    
    Parameters:
    ref - The reference to be added.
    
    Returns:
    True iff the reference was added to the cache and false iff the reference was found in a scan of the nscan MRU cache entries.
  - clear
```
public void clear(boolean clearRefs)
```
    Description copied from interface: IHardReferenceQueue
    
    Clears the cache (sets the head, tail and count to zero) without generating eviction notices.
    
    Specified by:
    
    clear in interface IHardReferenceQueue<T>
    
    Parameters:
    clearRefs - When true the references are explicitly set to null which can facilitate garbage collection.
  - evict
```
public boolean evict()
```
    Description copied from interface: IHardReferenceQueue
    
    Evict the LRU reference. This is a NOP iff the cache is empty.
    
    Specified by:
    
    evict in interface IHardReferenceQueue<T>
    
    Returns:
    true iff a reference was evicted.
    See Also:
    HardReferenceQueueEvictionListener
  - evictAll
```
public void evictAll(boolean clearRefs)
```
    Description copied from interface: IHardReferenceQueue
    
    Evict all references, starting with the LRU reference and proceeding to the MRU reference.
    
    Specified by:
    
    evictAll in interface IHardReferenceQueue<T>
    
    Parameters:
    clearRefs - When true, the reference are actually cleared from the cache. This may be false to force persistence of the references in the cache without actually clearing the cache.
  - peek
```
public T peek()
```
    Description copied from interface: IHardReferenceQueue
    
    The reference at the tail of the queue. This is the next reference that will be evicted from the queue.
    
    Specified by:
    
    peek in interface IHardReferenceQueue<T>
  - isEmpty
```
public boolean isEmpty()
```
    Description copied from interface: IHardReferenceQueue
    
    True iff the cache is empty.
    
    Specified by:
    
    isEmpty in interface IHardReferenceQueue<T>
  - isFull
```
public boolean isFull()
```
    Description copied from interface: IHardReferenceQueue
    
    True iff the cache is full.
    
    Specified by:
    
    isFull in interface IHardReferenceQueue<T>
  - scanHead
```
public boolean scanHead(int nscan,
               T ref)
```
  - scanTail
```
public boolean scanTail(int nscan,
               T ref)
```
  - size
```
public int size()
```
    Description copied from interface: IHardReferenceQueue
    
    The #of references in the cache. Note that there is no guarantee that the references are distinct.
    
    Specified by:
    
    size in interface IHardReferenceQueue<T>

Class SynchronizedHardReferenceQueue<T>

Field Summary

Fields inherited from interface com.bigdata.cache.IHardReferenceQueue

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

queue

Constructor Detail

SynchronizedHardReferenceQueue

SynchronizedHardReferenceQueue

Method Detail

beforeOffer

capacity

getListener

nscan

add

clear

evict

evictAll

peek

isEmpty

isFull

scanHead

scanTail

size