Trying to synchronize method within runnable

Question

I have a ConcurrentMap that gets instantiated outside of my runnables, but shared and updated within / accross the runnables. My runnables need to be concurrent, but my conc

Answer 1

Solution based on Sotirios Delimanolis, Luiggi Mendoza, Sotirios Delimanolis answer.

main

public class ExecutionSubmitExample {

    public static void main(String[] args) {
        ExecutorService es = Executors.newFixedThreadPool(10);

        List> tasks = new ArrayList<>();

        ConcurrentHashMap concurrentMap = new ConcurrentHashMap<>();

        for (int x = 0; x < 10; x++) {
            Example e = new Example(concurrentMap, x);
            Future future = es.submit(e, e);
            tasks.add(future);
        }
        // -- all threads should be launching, let's get the ExecutionSubmitExample objects



        try {
            for (Future future : tasks) {
                Example e = future.get();
            }

            for (Entry obj : concurrentMap.entrySet()) {
                System.out.println("key " + obj.getKey() + " " + obj.getValue());
            }
            es.shutdown();
        } catch (ExecutionException e) {
            throw new RuntimeException(e);
        } catch (InterruptedException ie) {
            throw new RuntimeException(ie);
        }
    }
}

runnable

public class Example implements Runnable {

    ConcurrentHashMap concurrentMap;
    private int thread;
    private final Object lock = new Object();

    public Example(ConcurrentHashMap concurrentMap, int thread) {
        this.concurrentMap = concurrentMap;
        this.thread = thread;
    }

    @Override
    public void run() {
        for (int i = 0; i < 3; i++) {
            runAnalysis(i);
        }
    }

    public void runAnalysis(int index) {
        synchronized(lock) {
            if(concurrentMap.containsKey(index)) {
                System.out.println("contains integer " + index);
            } else {
                System.out.println("put " + index + " thread " + thread);
                concurrentMap.put(index, "thread " + thread);
            }
        }
    }
}

results

put 0 thread 0
contains integer 0
put 1 thread 7
put 2 thread 7
contains integer 1
contains integer 2
contains integer 0
contains integer 1
contains integer 2
contains integer 0
contains integer 1
contains integer 2
contains integer 0
contains integer 1
contains integer 2
contains integer 0
contains integer 1
contains integer 2
contains integer 0
contains integer 1
contains integer 2
contains integer 0
contains integer 1
contains integer 2
contains integer 0
contains integer 1
contains integer 2
contains integer 0
contains integer 1
contains integer 2
key 0 thread 0
key 2 thread 7
key 1 thread 7