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package sun.misc;

ConditionLock is a Lock with a built in state variable.  This class
provides the ability to wait for the state variable to be set to a
desired value and then acquire the lock.

The lockWhen() and unlockWith() methods can be safely intermixed
with the lock() and unlock() methods. However if there is a thread
waiting for the state variable to become a particular value and you
simply call Unlock(), that thread will not be able to acquire the
lock until the state variable equals its desired value. 

Author:
     Peter King/**
 * ConditionLock is a Lock with a built in state variable.  This class
 * provides the ability to wait for the state variable to be set to a
 * desired value and then acquire the lock.<p>
 *
 * The lockWhen() and unlockWith() methods can be safely intermixed
 * with the lock() and unlock() methods. However if there is a thread
 * waiting for the state variable to become a particular value and you
 * simply call Unlock(), that thread will not be able to acquire the
 * lock until the state variable equals its desired value. <p>
 *
 * @author      Peter King
 */
public final
class ConditionLock extends Lock {
    private int state = 0;

    
Creates a ConditionLock.
/**
     * Creates a ConditionLock.
     */
    public ConditionLock () {
    }

    
Creates a ConditionLock in an initialState.
/**
     * Creates a ConditionLock in an initialState.
     */
    public ConditionLock (int initialState) {
        state = initialState;
    }

    
Acquires the lock when the state variable equals the desired state.
Params:
desiredState – the desired state
Throws:
InterruptedException – if any thread has
              interrupted this thread./**
     * Acquires the lock when the state variable equals the desired state.
     *
     * @param desiredState the desired state
     * @exception  java.lang.InterruptedException if any thread has
     *               interrupted this thread.
     */
    public synchronized void lockWhen(int desiredState)
        throws InterruptedException
    {
        while (state != desiredState) {
            wait();
        }
        lock();
    }

    
Releases the lock, and sets the state to a new value.
Params:
newState – the new state/**
     * Releases the lock, and sets the state to a new value.
     * @param newState the new state
     */
    public synchronized void unlockWith(int newState) {
        state = newState;
        unlock();
    }
}