fix.java

gistfile1.txt

import java.util.concurrent;

public class Ex2q1fix {
 
    private static class Peterson {
        private final AtomicIntegerArray flag = new AtomicIntegerArray(2);
        public volatile int victim;
 
        public void lock() throws InterruptedException {
            System.out.println("Aquiring lock for thread with id=" + threadLocalId.get());
            int i = threadLocalId.get();
            int j = 1 - i;
            flag.set(i, 1);
            victim = i;
            while (flag[j] && victim == i) {
                Thread.sleep(1);
            }
            System.out.println("Lock for thread with id=" + threadLocalId.get() + " aquired");
        }
 
        public void unlock() {
            int i = threadLocalId.get();
            flag.set(i, 0);
            System.out.println("Lock for thread with id=" + threadLocalId.get() + " released");
        }
    }
 
    static int counter = 0;
 
    static ThreadLocal<Integer> threadLocalId = new ThreadLocal<Integer>();
 
    public static void main(String[] args) throws InterruptedException {
        final Peterson counterLock = new Peterson();
        final int numberOfThreads = 2;
        Thread[] threads = new Thread[numberOfThreads];
        long start = System.currentTimeMillis();
        for (int i = 0; i < numberOfThreads; i++) {
            final Integer threadId = i;
            Thread thread = new Thread() {
                @Override
                public void run() {
                    System.out.println("Starting thread with id=" + threadId);
                    threadLocalId.set(threadId);
                    try {
                        for (int j = 0; j < 100000; j++) {
                            counterLock.lock();
                            try {
                                int localCounter = counter;
                                localCounter += 1;
                                System.out.println("Thread[" + threadId + "] counter=" + localCounter);
                                counter = localCounter;
                            } finally {
                                counterLock.unlock();
                            }
                        }
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            };
            thread.start();
            threads[i] = thread;
        }
 
        for (Thread thread : threads) {
            thread.join();
        }
        long duration = System.currentTimeMillis() - start;
        System.out.println(String.format("counter=%d duration=%d", counter, duration));
 
    }
}