You asked: What is ReentrantLock in Java?

What is a ReentrantLock?

A reentrant lock is one where a process can claim the lock multiple times without blocking on itself. It’s useful in situations where it’s not easy to keep track of whether you’ve already grabbed a lock.

How do you use ReentrantLock?

As the name says, ReentrantLock allows threads to enter into the lock on a resource more than once. When the thread first enters into the lock, a hold count is set to one. Before unlocking the thread can re-enter into lock again and every time hold count is incremented by one.

Why do we need ReentrantLock?

The thread doesn’t need to block infinitely, which was the case with synchronized. … ReentrantLock provides a convenient tryLock() method, which acquires lock only if its available or not held by any other thread. This reduces the blocking of thread waiting for lock-in Java applications.

What is the difference between ReentrantLock and synchronized?

In case of synchronized keyword, a thread can be blocked waiting for lock, for an indefinite period of time and there was no way to control that. ReentrantLock provides a method called lockInterruptibly(), which can be used to interrupt thread when it is waiting for lock.

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What is lockInterruptibly?

The lockInterruptibly() method locks the Lock unless the thread calling the method has been interrupted. Additionally, if a thread is blocked waiting to lock the Lock via this method, and it is interrupted, it exits this method calls.

What is deadlock in Java?

Deadlock describes a situation where two or more threads are blocked forever, waiting for each other. … A Java multithreaded program may suffer from the deadlock condition because the synchronized keyword causes the executing thread to block while waiting for the lock, or monitor, associated with the specified object.

Why do we need locks in Java?

A lock is a thread synchronization mechanism like synchronized blocks except locks can be more sophisticated than Java’s synchronized blocks. Locks (and other more advanced synchronization mechanisms) are created using synchronized blocks, so it is not like we can get totally rid of the synchronized keyword. … locks.

What is thread safe in Java?

thread-safety or thread-safe code in Java refers to code that can safely be utilized or shared in concurrent or multi-threading environment and they will behave as expected.

What is semaphore in Java?

A Semaphore is a thread synchronization construct that can be used either to send signals between threads to avoid missed signals, or to guard a critical section like you would with a lock. Java 5 comes with semaphore implementations in the java.

What is race condition Java?

Race condition in Java is a type of concurrency bug or issue that is introduced in your program because of parallel execution of your program by multiple threads at the same time, Since Java is a multi-threaded programming language hence the risk of Race condition is higher in Java which demands a clear understanding …

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How can we prevent deadlock in Java?

How can we avoid a deadlock in Java?

  1. Avoid Nested Locks: A deadlock mainly happens when we give locks to multiple threads. Avoid giving a lock to multiple threads if we already have given to one.
  2. Avoid Unnecessary Locks: We can have a lock only those members which are required. …
  3. Using Thread.

How do you acquire locked objects?

If a thread wants to execute then synchronized method on the given object. First, it has to get a lock-in that object. Once the thread got the lock then it is allowed to execute any synchronized method on that object. Once method execution completes automatically thread releases the lock.

Is synchronized in Java reentrant?

Synchronized blocks in Java are reentrant. This means, that if a Java thread enters a synchronized block of code, and thereby take the lock on the monitor object the block is synchronized on, the thread can enter other Java code blocks synchronized on the same monitor object.

What is public synchronized void in Java?

A synchronized block in Java is synchronized on some object. All synchronized blocks synchronized on the same object can only have one thread executing inside them at a time. All other threads attempting to enter the synchronized block are blocked until the thread inside the synchronized block exits the block.

What are the different types of locks in Java?

1. Types of Java locks

  • Optimistic lock / pessimistic lock.
  • Exclusive / shared lock.
  • Mutex / read / write lock.
  • Reentrant lock.
  • Fair lock / unfair lock.
  • Sectional lock.
  • Bias lock / lightweight lock / heavyweight lock.
  • Spinlock.
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