ExtensionId

java.lang.Object
- akka.actor.typed.ExtensionId<T>

Direct Known Subclasses:

ActorRefResolver$, Cluster$, ClusterSharding$, ClusterSingleton$, DistributedData$, DistributedData$, EventStreamExtension$, Receptionist$
```
public abstract class ExtensionId<T extends Extension>
extends java.lang.Object
```
Create the extension, will be invoked at most one time per actor system where the extension is registered.

Constructor Summary

Constructors
Constructor Description

ExtensionId()

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`T`	`apply(ActorSystem<?> system)`	Lookup or create an instance of the extension identified by this id.
`abstract T`	`createExtension(ActorSystem<?> system)`
`boolean`	`equals(java.lang.Object other)`
`int`	`hashCode()`
`ExtensionId<T>`	`id()`	Java API: The identifier of the extension

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

- Constructor Detail
  - ExtensionId
```
public ExtensionId()
```
- Method Detail
  - apply
```
public final T apply(ActorSystem<?> system)
```
    Lookup or create an instance of the extension identified by this id.
    
    Parameters:
    
    system - (undocumented)
    
    Returns:
    
    (undocumented)
  - createExtension
```
public abstract T createExtension(ActorSystem<?> system)
```
  - equals
```
public final boolean equals(java.lang.Object other)
```
    Overrides:
    
    equals in class java.lang.Object
  - hashCode
```
public final int hashCode()
```
    Overrides:
    
    hashCode in class java.lang.Object
  - id
```
public ExtensionId<T> id()
```
    Java API: The identifier of the extension
    
    Returns:
    
    (undocumented)