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.

What is the use of lock in Java?

locks. Lock is a thread synchronization mechanism just like synchronized blocks. A Lock is, however, more flexible and more sophisticated than a synchronized block. Since Lock is an interface, you need to use one of its implementations to use a Lock in your applications.

Why do we use locks?

A lock is a device used for raising and lowering boats, ships and other watercraft between stretches of water of different levels on river and canal waterways. … Locks are used to make a river more easily navigable, or to allow a canal to cross land that is not level.

Why do we need a read lock?

2 Answers. The point of a ReaderWriterLock is to make sure that no other thread mutates something while you read it. The read portion of the lock is not exclusive (there can be multiple concurrent readers), except with regard to the write portion (readers will wait for the writer and vice-versa).

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How can we prevent deadlock in Java?

How to avoid deadlock in java

  1. Avoid deadlock by breaking circular wait condition: In order to do that, you can make arrangement in the code to impose the ordering on acquisition and release of locks.
  2. Avoid Nested Locks: This is the most common reason for deadlocks, avoid locking another resource if you already hold one.

How does ConcurrentHashMap works in Java?

ConcurrentHashMap class is thread-safe i.e. multiple threads can operate on a single object without any complications. At a time any number of threads are applicable for a read operation without locking the ConcurrentHashMap object which is not there in HashMap. … The default concurrency-level of ConcurrentHashMap is 16.

How do I stop lock contention?

There are three ways to reduce lock contention:

  1. Reduce the duration for which locks are held;
  2. Reduce the frequency with which locks are requested; or.
  3. Replace exclusive locks with coordination mechanisms that permit greater concurrency.

Are canal locks dangerous?

But they face a serious risk of being sucked under by the powerful undertow, created when the gates open releasing more than a quarter of a million litres. The dangerous and illegal new craze also carries the risk of contracting Weil’s Disease – a potentially-fatal condition which can be caught from canal water.

How do locks work?

When the right key slides into a pin-and-tumbler lock, the pointed teeth and notches on the blade of the key allow the spring-loaded pins to move up and down until they line up with a track called the shear line. When the pins align with the shear line, the cylinder can turn and the lock will open.

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Can a mutex be locked more than once?

Can a mutex be locked more than once? A mutex is a lock. Only one state (locked/unlocked) is associated with it. However, a recursive mutex can be locked more than once (POSIX compliant systems), in which a count is associated with it, yet retains only one state (locked/unlocked).

Does READ need lock?

It is obviously necessary to lock the object when writing to it, as we do not want multiple threads to write to the object at the same time.

What are the two meanings of lock?

1a : a fastening (as for a door) operated by a key or a combination. b : the mechanism for exploding the charge or cartridge of a firearm. 2a : an enclosure (as in a canal) with gates at each end used in raising or lowering boats as they pass from level to level. b : air lock. 3a : a locking or fastening together.

How can we avoid deadlock situations?

Deadlocks can be prevented by preventing at least one of the four required conditions:

  1. 7.4.1 Mutual Exclusion. Shared resources such as read-only files do not lead to deadlocks. …
  2. 2 Hold and Wait. …
  3. 3 No Preemption. …
  4. 4 Circular Wait.

How can we solve deadlock?

A deadlock occurs when the first process locks the first resource at the same time as the second process locks the second resource. The deadlock can be resolved by cancelling and restarting the first process.

How do you handle deadlock situations?

Deadlock is a situation where a process or a set of processes is blocked, waiting for some other resource that is held by some other waiting process.

Handling Deadlocks

  1. Mutual Exclusion – A resource can be used by only one process at a time. …
  2. Hold and wait – …
  3. No pre-emption – …
  4. Circular wait –
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