CloseableThreadLocal (core 2.2.0-alpha04 API)

java.lang.Object
- org.neo4j.gds.utils.CloseableThreadLocal<T>

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable
```
public class CloseableThreadLocal<T>
extends java.lang.Object
implements java.io.Closeable
```
Java's builtin ThreadLocal has a serious flaw: it can take an arbitrarily long amount of time to dereference the things you had stored in it, even once the ThreadLocal instance itself is no longer referenced. This is because there is single, master map stored for each thread, which all ThreadLocals share, and that master map only periodically purges "stale" entries. While not technically a memory leak, because eventually the memory will be reclaimed, it can take a long time and you can easily hit OutOfMemoryError because from the GC's standpoint the stale entries are not reclaimable. This class works around that, by only enrolling WeakReference values into the ThreadLocal, and separately holding a hard reference to each stored value. When you call close(), these hard references are cleared and then GC is freely able to reclaim space by objects stored in it. We can not rely on ThreadLocal.remove() as it only removes the value for the caller thread, whereas close() takes care of all threads. You should not call close() until all threads are done using the instance.

Field Summary

Fields
Modifier and Type Field Description

protected java.lang.ThreadLocal<java.lang.ref.WeakReference<T>> t

Constructor Summary

Constructors
Constructor Description

CloseableThreadLocal(java.util.function.Supplier<T> constructor)

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`close()`
`T`	`get()`
`protected T`	`initialValue()`
`void`	`set(T object)`
`static <T> CloseableThreadLocal<T>`	`withInitial(java.util.function.Supplier<T> initialValueSupplier)`

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

Field Detail

t

protected java.lang.ThreadLocal<java.lang.ref.WeakReference<T>> t

Constructor Detail

CloseableThreadLocal

public CloseableThreadLocal(java.util.function.Supplier<T> constructor)

Method Detail

withInitial

public static <T> CloseableThreadLocal<T> withInitial(java.util.function.Supplier<T> initialValueSupplier)

initialValue
```
protected T initialValue()
```

get
```
public T get()
```

set
```
public void set(T object)
```

close
```
public void close()
```
Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable