Java Thread How to - Use ReadWriteLock on Variable

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Question

We would like to know how to use ReadWriteLock on Variable.

Answer

import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
//from  w  w w  .ja v a2  s. com
abstract class ThreadSafeWrapper<T> {
  ReadWriteLock lock = new ReentrantReadWriteLock();
  T object;

  public ThreadSafeWrapper(T object) {
    this.object = object;
  }

  public final void methodOneWriteLock(String var) {
    lock.writeLock().lock();
    try {
      doMethodOne(object, var);
    } finally {
      lock.writeLock().unlock();
    }
  }

  public final void methodTwoReadLock(String var) {
    lock.readLock().lock();
    try {
      doMethodTwo(object, var);
    } finally {
      lock.readLock().unlock();
    }
  }

  abstract void doMethodOne(T obj, String var);

  abstract void doMethodTwo(T obj, String var);
}

public class Main {
  public static void main(String[] args) {
    ThreadSafeWrapper<String> wrapper = new ThreadSafeWrapper<String>("lala") {
      @Override
      protected void doMethodOne(String obj, String var) {
        System.out.println("method one: " + obj + " " + var);
      }

      @Override
      protected void doMethodTwo(String obj, String var) {
        System.out.println("method two: " + obj + " " + var);
      }
    };
    wrapper.methodOneWriteLock("foo");
    wrapper.methodTwoReadLock("bar");
  }
}

The code above generates the following result.

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