Tuesday, May 10, 2022

StampedLock With Examples

  StampedLock :  StampedLock was introduced in Java 8. It also supports read and write locks. However, lock acquisition methods return a stamp that will be used to release a lock or to check if the lock is still valid:
public class StampedLock
extends Object
implements Serializable
It also supports both read and write locks. It is a capability-based lock with three modes for controlling read/write access. The state of a StampedLock consists of a version and mode.
  • Writing.
  • Reading.
  • Optimistic Reading.
  • ReadWriteLock use only two mode readLock and writeLock
  • Stampedlock use three mode readLock, writeLock and Optimism lock
  • StampedLocks returns the stamps that are long values which is used to unlock readLock or writeLock.
  • Stampedlock is faster than ReadWriteLock
  • StampedLock Don't like ReadWriteLock, It's not reentrant 
  • StampedLock can convert lock, readLock to writeLock OR writeLock to readLock using tryConvertToReadLock, tryConvertToWriteLock
  • Note that we can convert readLock to writeLock when only single thread acquired readLock using tryConvertToWriteLock. it will not convert to writeLock if multiple thread acquired readLock.
  • writeLock can be converted to readLock using tryConvertToReadLock even we are triying go get multiple writeLock because only one writeLock can be acquired at a time.

public long writeLock() : This is same like ReadWriteLock. It is Exclusively acquires the lock, it is blocking if necessary until available. 

public long tryWriteLock() : Exclusively acquires the lock if it is immediately available.

public long tryWriteLock(long time, TimeUnit unit) : Exclusively acquires the lock if it is available if not available wait for given time. 

public boolean tryUnlockWrite() : Releases the writeLock if it is currently held.

public boolean isWriteLocked() : Return true if the  writeLock is currently held exclusively. 

public long readLock()

public long tryReadLock()

public long tryReadLock(long time, TimeUnit unit)

public long tryUnlockRead()

public long unlock(long stamp)



 tryConvertToReadLock : Using tryConvertToReadLock we can convert writeLock to readLock.

tryConvertToWriteLock : Using tryConvertToWriteLock we can convert readLock to writeLock but it can convert to writeLock if only one readLock. if multple readLock is there than it will not convert to writeLock.





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