java ReentrantReadWriteLock

// read and write lock is mutual exclusion lock
//Listing 7-3. Using ReadWriteLock to Satisfy a Dictionary Application’s Reader and
//Writer Threads
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class A
{
    public static void main(String[] args)
    {
        final String[] words =
        {
        "hypocalcemia",
        "prolixity",
        "assiduous",
        "indefatigable",
        "castellan"
        };
        final String[] definitions =
        {
        "a deficiency of calcium in the blood",
        "unduly prolonged or drawn out",
        "showing great care, attention, and effort",
        "able to work or continue for a lengthy time without tiring",
        "the govenor or warden of a castle or fort"
        };
 
        final Map<String, String> dictionary = new HashMap<String, String>();
        ReadWriteLock rwl = new ReentrantReadWriteLock(true);
        final Lock rlock = rwl.readLock();
        final Lock wlock = rwl.writeLock();
        Runnable writer = () ->
        {
                for (int i = ; i < words.length; i++)
                {
                    wlock.lock();
                    try
                    {
                        dictionary.put(words[i],definitions[i]);
                        System.out.println("writer storing " +words[i] + " entry");
                    }
                    finally
                    {
                        wlock.unlock();
                    }
 
                    try
                    {
                    Thread.sleep();
                    }
                    catch (InterruptedException ie)
                    {
                    System.err.println("writer " +
                    "interrupted");
                    }
                }
        };
 
        ExecutorService es = Executors.newFixedThreadPool();
        es.submit(writer);
 
        Runnable reader = () ->
        {
            while (true)
            {
                    rlock.lock();
                    try
                    {
                        int i = (int) (Math.random() *    words.length);
                                System.out.println("reader accessing " + words[i] + ": " +dictionary.get(words[i])
                                + " entry");
                    }
                    finally
                    {
                    rlock.unlock();
                    }
            }
         };
 
    es = Executors.newFixedThreadPool();
    es.submit(reader);
    }
}