Question about running Multiple Threads

[ferdzz]

Hi all,

I am working on an exercise that tells me:

Assume that in the class that you are currently writing, there is already a method long calculate() that returns a long value produced by an algorithm that takes an unpredictable time to finish.
Write a method void sum(int n) that launches a total of n new threads, each of which calls this method calculate, and after all these threads have finished, your method sum returns the sum of values that were produced by these n calls.

I have written my code, I need is confirmation if the code is logically and syntactically correct. Thanks in advance.

Here are my instance fields

        private volatile boolean running = true;
	private static Object mutex;
	private static ArrayList <Sums> sum = new ArrayList<Sums>();
	private double total;

And my sum method

	
        public void sum(int n){
		for (int i = 0; i < n; i++){
			new Thread(new Runnable(){
				public void run() {
					try{
						while(running){
							synchronized(mutex){
								this.wait();
								for (Sums e: sum){
									calculate();
									total += e;
								}		
							}
						}
					}catch (InterruptedException e){}
				}
			}).start();
		} System.out.print(total);
	}

There is also one syntax error, on the line "total += e;" and there were no suggestions on Eclipse on how to fix it. Any help is greatly appreciated.

[JosAH]

There is also one syntax error, on the line "total += e;" and there were no suggestions on Eclipse on how to fix it. Any help is greatly appreciated.

Variable 'e' has type Sums; you can only use the'+' operator on primitive numeric types (ints, doubles etc) and Strings (the latter is a little compiler trick).

kind regards,

Jos

[Norm]

Add a method to the Sums class to return its value as double.