Sommatore.java

import java.util.*;

public class Sommatore{
	public class Somma{
		public int a, b, result;

		public Somma(int a, int b){
			this.a = a;
			this.b = b;
			result = 0;
		}
	}

	private ArrayList<Somma> somme = new ArrayList<>();
	private int index = 0;

	public void addSomma(int a, int b){
		synchronized(somme){
			somme.add(new Somma(a, b));
		}
	}

	private void threadRunner(){
		while(true){
			Somma s;
			synchronized(somme){
				if(index >= somme.size())
					return;
				s = somme.get(index++);
			}
			s.result = s.a + s.b;
		}
	}

	public void calcola(int numThreads){
		Thread[] t = new Thread[numThreads];
		for(int i = 0; i < numThreads; i++){
			t[i] = new Thread(new Runnable(){
				public void run(){
					threadRunner();
				}
			});
		}
		for(int i = 0; i < numThreads; i++){
			t[i].start();
		}
		for(int i = 0; i < numThreads; i++){
			try{
				t[i].join();
			}catch(InterruptedException ex){

			}
		}
	}

	public ArrayList<Somma> getSomme(){
		return somme;
	}

	//Uso: java sommatore <numero interi> <numero thread>
	public static void main(String[] args){
		if(args.length < 2){
			System.out.println("Usage: java sommatore <num integers> <num threads>");
			return;
		}
		Sommatore sm = new Sommatore();
		Random r = new Random();
		int ints = Integer.parseInt(args[0]);
		int threads = Integer.parseInt(args[1]);
		for(int i = 0; i < ints; i++){
			sm.addSomma(r.nextInt(), r.nextInt());
		}
		sm.calcola(threads);
		ArrayList<Somma> somme = sm.getSomme();
		for(Somma s : somme){
			System.out.println("Somma: " + s.a + " + " + s.b + " = " + s.result);
		}
	}
}