Functions.WeakMemoizer

java.lang.Object
- io.atlassian.fugue.Functions.WeakMemoizer<A,B>

Type Parameters:

A - comparable descriptor, the usual rules for any HashMap key apply.

B - the value

All Implemented Interfaces:

java.util.function.Function<A,B>

Enclosing class:

Functions
```
static final class Functions.WeakMemoizer<A,B>
extends java.lang.Object
implements java.util.function.Function<A,B>
```
Class supports the implementation of Functions.weakMemoize(Function) and is not intended for general use. Functions.WeakMemoizer caches the result of another function. The result is weakly referenced internally. This is useful if the result is expensive to compute or the identity of the result is particularly important.
If the results from this function are further cached then they will tend to stay in this cache for longer.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`(package private) static class`	`Functions.WeakMemoizer.MappedReference<K,V>`	A weak reference that maintains a reference to the key so that it can be removed from the map when the value is garbage collected.

Field Summary

Fields
Modifier and Type	Field	Description
`private java.util.function.Function<A,B>`	`delegate`
`private java.util.concurrent.ConcurrentMap<A,Functions.WeakMemoizer.MappedReference<A,B>>`	`map`
`private java.lang.ref.ReferenceQueue<B>`	`queue`

Constructor Summary

Constructors
Constructor Description

WeakMemoizer(java.util.function.Function<A,B> delegate)
Construct a new Functions.WeakMemoizer instance.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`B`	`apply(A descriptor)`	Get a result for the supplied Descriptor.
`private void`	`expungeStaleEntries()`
`(package private) static <A,B> Functions.WeakMemoizer<A,B>`	`weakMemoizer(java.util.function.Function<A,B> delegate)`

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

Methods inherited from interface java.util.function.Function
andThen, compose

Field Detail

map

private final java.util.concurrent.ConcurrentMap<A,Functions.WeakMemoizer.MappedReference<A,B>> map

queue

private final java.lang.ref.ReferenceQueue<B> queue

delegate

private final java.util.function.Function<A,B> delegate

Constructor Detail
- WeakMemoizer
```
WeakMemoizer(java.util.function.Function<A,B> delegate)
```
  Construct a new Functions.WeakMemoizer instance.
  
  Parameters:
  
  delegate - for creating the initial values.

Method Detail
- weakMemoizer
```
static <A,B> Functions.WeakMemoizer<A,B> weakMemoizer(java.util.function.Function<A,B> delegate)
```
- apply
```
public B apply(A descriptor)
```
  Get a result for the supplied Descriptor.
  
  Specified by:
  
  apply in interface java.util.function.Function<A,B>
  
  Parameters:
  
  descriptor - must not be null
  
  Returns:
  
  descriptor lock
- expungeStaleEntries
```
private void expungeStaleEntries()
```