Reentrant ReadWriteLock example of value calculator

Byron KiourtzoglouNovember 11th, 2012Last Updated: June 19th, 2013

0 90 1 minute read

This is an example of how to use a ReentrantReadWriteLock of a value calculator. We have implemented a method that uses a ReadWriteLock and implements the calculate(int value), the getCalculatedValue() and the getValue() methods. In short the class is described below:

It creates a ReentrantReadWriteLock.
First it calls calculate(int value) with the int value that is to be calculated. The method acquires the lock used for writing, using writeLock() API method of ReadWriteLock and lock() API method of Lock. After acquiring the lock, this method calculates the value. Finally the method releases the lock, using writeLock() API method of ReadWriteLock and unlock() API method of Lock.
The getCalculatedValue() method returns the calculated value. It gets the lock used for reading, using readLock() API method of ReadWriteLock and lock() API method of Lock. It returns the calculated value and then releases the lock, using readLock() API method of ReadWriteLock and unlock() API method of Lock.
The getValue() method of the class returns the initial value, using readLock() API method of ReadWriteLock and lock() API method of Lock to get the lock and then releases the lock, using readLock() API method of ReadWriteLock and unlock() API method of Lock.

Let’s take a look at the code snippet that follows:

public class Calculator {
    private int calculatedValue;
    private int value;
    private ReadWriteLock lock = new ReentrantReadWriteLock();
 
    public void calculate(int value) {

  lock.writeLock().lock();

  try {


this.value = value;


this.calculatedValue = doMySlowCalculation(value);

  } finally {


lock.writeLock().unlock();

  }
    }
 
    public int getCalculatedValue() {

  lock.readLock().lock();

  try {


return calculatedValue;

  } finally {


lock.readLock().unlock();

  }
    }
 
    public int getValue() {

  lock.readLock().lock();

  try {


return value;

  } finally {


lock.readLock().unlock();

  }
    }
}

This was an example of how to use a ReentrantReadWriteLock of a value calculator in Java.

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