Package org.apache.hadoop.hbase.util

Class FastStringPool

java.lang.Object

org.apache.hadoop.hbase.util.FastStringPool

@Private
public class FastStringPool
extends Object

A string pool like String.intern(), but more flexible as we can create multiple instances and use them in difference places, where String.intern() is global.

We use WeakReference so when there are no actual reference to the String, it will be GCed to reduce memory pressure.

The difference between WeakObjectPool is that, we also need to use WeakReference as key, not only value, because the key(a String) is exactly what we want to deduplicate.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static final class	FastStringPool.WeakKey

Field Summary

Fields

Modifier and Type	Field	Description
private static final int	CLEANUP_MASK
private final Lock	cleanupLock
private final AtomicInteger	counter
private final ConcurrentHashMap<FastStringPool.WeakKey,WeakReference<String>>	map
private final ReferenceQueue<String>	refQueue

Constructor Summary

Constructors

Constructor	Description
FastStringPool()

Method Summary

Modifier and Type	Method	Description
private void	cleanup()
String	intern(String s)
private void	maybeCleanup()
int	size()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

map

private final ConcurrentHashMap<FastStringPool.WeakKey,WeakReference<String>> map

refQueue

private final ReferenceQueue<String> refQueue

cleanupLock

private final Lock cleanupLock

CLEANUP_MASK

private static final int CLEANUP_MASK

See Also:

• Constant Field Values

counter

private final AtomicInteger counter

Constructor Details

FastStringPool

public FastStringPool()

Method Details

intern

public String intern(String s)

cleanup

private void cleanup()

maybeCleanup

private void maybeCleanup()

size

public int size()