Package org.apache.lucene.util

Class SetOnce<T>

java.lang.Object

org.apache.lucene.util.SetOnce<T>

All Implemented Interfaces:

Cloneable

public final class SetOnce<T>
extends Object
implements Cloneable

A convenient class which offers a semi-immutable object wrapper implementation which allows one to set the value of an object exactly once, and retrieve it many times. If set(Object) is called more than once, SetOnce.AlreadySetException is thrown and the operation will fail.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	SetOnce.AlreadySetException	Thrown when set(Object) is called more than once.

Constructor Summary

Constructors

Constructor	Description
SetOnce()	A default constructor which does not set the internal object, and allows setting it by calling set(Object).
SetOnce(T obj)	Creates a new instance with the internal object set to the given object.

Method Summary

Modifier and Type	Method	Description
T	get()	Returns the object set by set(Object).
void	set(T obj)	Sets the given object.
boolean	trySet(T obj)	Sets the given object if none was set before.

Methods inherited from class java.lang.Object

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

Constructor Details

SetOnce

public SetOnce()

A default constructor which does not set the internal object, and allows setting it by calling set(Object).

SetOnce

public SetOnce(T obj)

Creates a new instance with the internal object set to the given object. Note that any calls to set(Object) afterwards will result in SetOnce.AlreadySetException

Throws:

SetOnce.AlreadySetException - if called more than once

See Also:

• set(Object)

Method Details

set

public void set(T obj)

Sets the given object. If the object has already been set, an exception is thrown.

trySet

public boolean trySet(T obj)

Sets the given object if none was set before.

Returns:

true if object was set successfully, false otherwise

get

public T get()

Returns the object set by set(Object).