SingletonMap.SingletonHolder

java.lang.Object
- nonapi.io.github.classgraph.concurrency.SingletonMap.SingletonHolder<V>

Type Parameters:

V - the singleton type

Enclosing class:

SingletonMap<K,V,E extends java.lang.Exception>
```
private static class SingletonMap.SingletonHolder<V>
extends java.lang.Object
```
Wrapper to allow an object instance to be put into a ConcurrentHashMap using putIfAbsent() without requiring the instance to be initialized first, so that putIfAbsent can be performed without wrapping it with a synchronized lock, and so that initialization work is not wasted if an object is already in the map for the key.

Field Summary

Fields
Modifier and Type	Field	Description
`private java.util.concurrent.CountDownLatch`	`initialized`	Whether or not the singleton has been initialized (the count will have reached 0 if so).
`private V`	`singleton`	The singleton.

Constructor Summary

Constructors
Modifier Constructor Description

private SingletonHolder()

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`(package private) V`	`get()`	Get the singleton value.
`(package private) void`	`set(V singleton)`	Set the singleton value, and decreases the countdown latch to 0.

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

- Field Detail
  - singleton
```
private volatile V singleton
```
    The singleton.
  - initialized
```
private final java.util.concurrent.CountDownLatch initialized
```
    Whether or not the singleton has been initialized (the count will have reached 0 if so).
- Constructor Detail
  - SingletonHolder
```
private SingletonHolder()
```
- Method Detail
  - set
```
void set(V singleton)
  throws java.lang.IllegalArgumentException
```
    Set the singleton value, and decreases the countdown latch to 0.
    
    Parameters:
    
    singleton - the singleton
    
    Throws:
    
    java.lang.IllegalArgumentException - if this method is called more than once (indicating an internal inconsistency).
  - get
```
V get()
throws java.lang.InterruptedException
```
    Get the singleton value.
    
    Returns:
    
    the singleton value.
    
    Throws:
    
    java.lang.InterruptedException - if the thread was interrupted while waiting for the value to be set.