Module org.microbean.lang

Package org.microbean.lang

Class CompletionLock

java.lang.Object

org.microbean.lang.CompletionLock

public final class CompletionLock
extends Object

A utility class logically containing a single Lock that is used to guard against concurrent symbol completion.

The javax.lang.model.* classes make no guarantees about thread safety. Certain operations on TypeMirror and Element, particularly TypeMirror.getKind() and Element.getKind() operations, will result in symbol completion, which may involve modification of the TypeMirror or Element in question. It is imperative that this modification be performed under global lock if thread safety is to be preserved, and that is the function of this class.

Note that DelegatingTypeMirror and DelegatingElement automatically perform such locking, and all operations in Lang that could result in symbol completion also perform such locking.

Author:

Laird Nelson

See Also:

• acquire()
• release()

Method Summary

Modifier and Type	Method	Description
static final Lock	acquire()	Calls lock() on the global Lock and returns it.
static final void	guard(Runnable r)	Calls acquire(), then run() on the supplied Supplier, then release() in a finally block.
static final boolean	guard(BooleanSupplier s)	Calls acquire(), then get() on the supplied BooleanSupplier, then release() in a finally block, and returns the result of the getAsBoolean() invocation.
static final <T> T	guard(Supplier<? extends T> s)	Calls acquire(), then get() on the supplied Supplier, then release() in a finally block, and returns the result of the get() invocation.
static final Lock	release()	Calls unlock() on the global Lock and returns it.

Methods inherited from class java.lang.Object

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

Method Details

acquire

public static final Lock acquire()

Calls lock() on the global Lock and returns it.

Returns:

the locked Lock; never null

See Also:

• release()

release

public static final Lock release()

Calls unlock() on the global Lock and returns it.

Returns:

the unlocked Lock; never null

See Also:

• acquire()

guard

public static final <T> T guard(Supplier<? extends T> s)

Calls acquire(), then get() on the supplied Supplier, then release() in a finally block, and returns the result of the get() invocation.

Type Parameters:

T - the type of the object this method will return

Parameters:

s - a Supplier; must not be null

Returns:

the result of an invocation of the supplied Supplier's get() method, which may be null

Throws:

NullPointerException - if s is null

guard

public static final boolean guard(BooleanSupplier s)

Calls acquire(), then get() on the supplied BooleanSupplier, then release() in a finally block, and returns the result of the getAsBoolean() invocation.

Parameters:

s - a BooleanSupplier; must not be null

Returns:

the result of an invocation of the supplied BooleanSupplier's getAsBoolean() method

Throws:

NullPointerException - if s is null

guard

public static final void guard(Runnable r)

Calls acquire(), then run() on the supplied Supplier, then release() in a finally block.

Parameters:

r - a Runnable; must not be null

Throws:

NullPointerException - if r is null