The java.util.concurrent.locks
package in Java provides a framework for locking and synchronization that may be more flexible and powerful than the built-in Java synchronization mechanisms. The Lock
interface in this package defines a set of methods for locking and unlocking objects, and the ReentrantLock
class provides a concrete implementation of this interface.
In addition to the Lock
interface and ReentrantLock
class, the java.util.concurrent.locks
package contains a number of other useful classes and interfaces for working with locks and synchronization, including the Condition
interface, the ReadWriteLock
interface, and the ReentrantReadWriteLock
class.
The Lock
interface defines a set of methods for locking and unlocking objects. The ReentrantLock
class is a concrete implementation of this interface.
To create a ReentrantLock
object, you can use the following code:
ReentrantLock lock = new ReentrantLock();
To lock an object, you can use the lock
method:
lock.lock();
To unlock an object, you can use the unlock
method:
lock.unlock();
It is important to note that you should always unlock an object in the finally block of a try-catch-finally statement to ensure that the object is always unlocked even if an exception is thrown:
try {
lock.lock();
// Perform some actions here.
} finally {
lock.unlock();
}
The Condition
interface defines a set of methods for waiting and signaling threads. A Condition
object is associated with a Lock
object and can be used to synchronize the execution of threads.
To create a Condition
object, you can use the following code:
Condition condition = lock.newCondition();
To wait for a condition, you can use the await
method:
condition.await();
To signal a condition, you can use the signal
method:
condition.signal();
It is important to note that you should always call the signal
method in the finally block of a try-catch-finally statement to ensure that the condition is always signaled even if an exception is thrown:
try {
// Perform some actions here.
} finally {
condition.signal();
}
The ReadWriteLock
interface defines a set of methods for locking and unlocking objects for reading and writing. The ReentrantReadWriteLock
class is a concrete implementation of this interface.
To create a ReentrantReadWriteLock
object, you can use the following code:
ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
To lock an object for reading, you can use the readLock
method:
lock.readLock().lock();
To unlock an object for reading, you can use the readLock
method:
lock.readLock().unlock();
To lock an object for writing, you can use the writeLock
method:
lock.writeLock().lock();
To unlock an object for writing, you can use the writeLock
method:
lock.writeLock().unlock();
It is important to note that you should always unlock an object in the finally block of a try-catch-finally statement to ensure that the object is always unlocked even if an exception is thrown:
try {
lock.writeLock().lock();
// Perform some actions here.
} finally {
lock.writeLock().unlock();
}
The java.util.concurrent.locks
package in Java provides a framework for locking and synchronization that may be more flexible and powerful than the built-in Java synchronization mechanisms. The Lock
interface in this package defines a set of methods for locking and unlocking objects, and the ReentrantLock
class provides a concrete implementation of this interface.
In addition to the Lock
interface and ReentrantLock
class, the java.util.concurrent.locks
package contains a number of other useful classes and interfaces for working with locks and synchronization, including the Condition
interface, the ReadWriteLock
interface, and the ReentrantReadWriteLock
class.