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// XXX uses: FolderChildren, Children.MutexChildren, module system
// XXX lock wrapper for AbstractDocument (or Document + NbDocument.WriteLockable)
package threaddemo.locking;
/**
* Factory for locks.
* @author Ales Novak (old code), Jesse Glick (rewrite - #32439)
*/
public class Locks {
private Locks() {}
/**
* Pseudo-lock that allows code to be synchronized with the AWT event dispatch thread.
* This is handy in that you can define a constant of type Lock in some API, initially
* set to a normal lock, and then switch everything to the event thread (or vice-versa).
* <p>It behaves somewhat differently from a read-write lock.
* <ol>
* <li>There is no distinction between read and write access. There is only one
* access mode, which is exclusive, and runs on the AWT thread, not in the
* caller thread.
* <li>There is no {@link PrivilegedLock}, so you cannot make entry or exit calls
* by themselves (which would make no sense).
* <li>You cannot specify a level. The event lock is considered to be at a higher
* level than any ordinary lock with a defined level. This means that from the
* event thread, you can enter any lock (subject to other restrictions), but
* while holding any <em>ordered</em> lock you may not block on the event thread
* (using <code>Locks.eventLock</code> methods).
* <li>{@link Lock#read(LockAction)}, {@link Lock#read(LockExceptionAction)},
* {@link Lock#write(LockAction)}, {@link Lock#write(LockExceptionAction)},
* {@link Lock#read(Runnable)}, and {@link Lock#write(Runnable)} when called from the
* event thread run synchronously. Else they all block, like
* {@link java.awt.EventQueue#invokeAndWait}.
* <li>{@link Lock#readLater(Runnable)} and {@link Lock#writeLater(Runnable)} run asynchronously, like
* {@link java.awt.EventQueue#invokeLater}.
* <li>{@link Lock#canRead} and {@link Lock#canWrite} just test whether you are in the event
* thread, like {@link java.awt.EventQueue#isDispatchThread}.
* </ol>
*/
public static RWLock event() {
return EventLock.DEFAULT;
}
/**
* XXX
*/
public static synchronized RWLock eventHybrid() {
return EventHybridLock.DEFAULT;
}
/**
* XXX
*/
public static RWLock monitor(Object monitor) {
return new MonitorLock(monitor);
}
/**
* Create a read/write lock.
* Allows control over resources that
* can be read by several readers at once but only written by one writer.
* Wrapper for {@link java.util.concurrent.locks.ReentrantReadWriteLock}.
*/
public static RWLock readWrite() {
return new ReadWriteLockWrapper();
}
/**
* Create a lock with a privileged key.
* @param privileged a key which may be used to call unbalanced entry/exit methods directly
* @see #readWrite()
*/
public static RWLock readWrite(PrivilegedLock privileged) {
DuplexLock l = (DuplexLock) readWrite();
privileged.setParent(l);
return l;
}
}
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