#jjs :call Java from js

counter.js

// mutex implemented by synchornized keyword
var Mutex = Packages.Mutex;
// Java native mutex
var Lock = java.util.concurrent.locks.ReentrantLock;

var Thread = java.lang.Thread
var mutex = new Mutex(); // or = new Lock();
var sum = 0;

function adder(c) {
  return function () {
    while (c > 0) {
      c -= 1;
      mutex.lock();
      sum += 1;
      mutex.unlock();
    }
  }
}

function newThread(func, name) {
  return new Thread(function run() {
    print("thread " + name + " started");
    func();
    print("thread " + name + " ended");
  });
}

var t1 = newThread(adder(10), "t1");
var t2 = newThread(adder(100), "t2");
var t3 = newThread(adder(1000), "t3");
var t4 = newThread(adder(10000), "t4");
t1.start();
t3.start();
t2.start();
t4.start();

//while (true) {
  //Thread.sleep(1000);
  //print("t1 " + t1.state);
  //print("t2 " + t2.state);
  //print("t3 " + t3.state);
  //if (
        //String(t1.state) == 'TERMINATED' &&
        //String(t2.state) == 'TERMINATED' &&
        //String(t3.state) == 'TERMINATED'
     //) {
    //break;
  //}
//}

t1.join(); t2.join(); t3.join(); t4.join();
print("sum = " + sum)

jjs_mutex

// mutex implemented by synchornized keyword
var Mutex = Packages.Mutex;
// Java native mutex
var Lock = java.util.concurrent.locks.ReentrantLock;

var Thread = java.lang.Thread
var mutex = new Mutex(); // or = new Lock();
var sum = 0;

function adder(c) {
  return function () {
    while (c > 0) {
      c -= 1;
      mutex.lock();
      sum += 1;
      mutex.unlock();
    }
  }
}

function newThread(func, name) {
  return new Thread(function run() {
    print("thread " + name + " started");
    func();
    print("thread " + name + " ended");
  });
}

var t1 = newThread(adder(10), "t1");
var t2 = newThread(adder(100), "t2");
var t3 = newThread(adder(1000), "t3");
var t4 = newThread(adder(10000), "t4");
t1.start();
t3.start();
t2.start();
t4.start();

//while (true) {
  //Thread.sleep(1000);
  //print("t1 " + t1.state);
  //print("t2 " + t2.state);
  //print("t3 " + t3.state);
  //if (
        //String(t1.state) == 'TERMINATED' &&
        //String(t2.state) == 'TERMINATED' &&
        //String(t3.state) == 'TERMINATED'
     //) {
    //break;
  //}
//}

t1.join(); t2.join(); t3.join(); t4.join();
print("sum = " + sum)

Makefile

run: Mutex.class
	jjs -cp . counter.js

Mutex.class: Mutex.java
	javac Mutex.java


.PHONY: run

Mutex.java

import java.util.HashSet;

public class Mutex {
    private boolean isLocked = false;
    private long ownerId = 0;

    public synchronized void lock() {
        while (isLocked) {
            try {
                wait();
            } catch (InterruptedException e) {}
        }
        isLocked = true;
        ownerId = Thread.currentThread().getId();
    }

    public synchronized void unlock() {
        if (ownerId != Thread.currentThread().getId()) {
            throw new RuntimeException("try to unlock a mutex not locked by me");
        }
        ownerId = 0;
        isLocked = false;
        notifyAll();
    }
}