// 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);
}
}