/* A simple demonstration of race conditions
   and how to use synchronized to avoid them
*/

public class MultiThreadedCounter01 implements Runnable {


    private int n; /* how many times to increment */
    private boolean useSynchronized; /* whether to use synchronized methods or not */
    
    private int count = 0; /* we accumulate a count */


    /** return the count 
     @return count of how many times incr has been called (supposedly) */

    public int getCount() { return count; }

    public void reset() { 
	count = 0;
    }

    /** Increment count as quickly as Java allows.
     */

    public void incr() { 
	    count++; /* Equivalent to count = count + 1; */ 
    } 


    /** Increment count as quickly as Java allows.
     */

    public synchronized void incrSync() { count++; /* Equivalent to count = count + 1; */ }



    /** Create a thread that will increment count n times.

       @param n How many times to increment
       @param useSynchronized  Whether to use Synchronized methods
    */


    public MultiThreadedCounter01(int n, boolean sync) {
	this.n = n;
	this.useSynchronized = sync;
    }
    
    /* run the thread and do the work of incrementing n times
     */

    public void run () {
	for (int i=0; i<this.n; i++) {
	    if (useSynchronized) {
		incrSync();
	    } else {
		incr();
	    }
	} // for
    } // run

    public static void main(String [] args) {

	if (args.length != 2) {
	    System.err.println("Usage: java MultiThreadedCounter01 n sync\n" +
			       "  n: number of times to increment per thread\n" +
			       "  sync: T or t for true, anything else for false\n" );
	    System.exit(1);
	}

	int n = Integer.parseInt(args[0]);
	boolean sync = (args[1].charAt(0)=='T' || args[1].charAt(0)=='t');

	System.out.printf("n=%d sync=%b\n", 
			  n, 
			  sync);			  

	MultiThreadedCounter01 mtc = new MultiThreadedCounter01(n, sync);
	Thread t1 = new Thread(mtc);
	Thread t2 = new Thread(mtc);
	System.out.println("In main: About to start threads");
	t1.start();
	t2.start();
	System.out.println("In main: just started threads... waiting for t1 to finish.");

	try {
	    t1.join();
	    System.out.println("In main: t1 finished... waiting for t2 to finish.");
	    t2.join();
	    System.out.println("In main: t2 is finished");
	} catch (InterruptedException ie) {
	    System.out.println(ie);
	    ie.printStackTrace();
	}
	System.out.printf("count=%d\n", mtc.getCount());
    }
}