gistfile1.java

/**
     * Multi-threaded matrix multiplication.
     * @param a a matrix
     * @param b another matrix
     * @return The resulting matrix-multiplied matrix
     */
    public static int[][] multiplyMatrix(final int[][] a, final int[][] b) {
        ExecutorService exec = Executors.newFixedThreadPool(9);
        List<Callable<Object>> tasks = new LinkedList<>();
        final int[][] result = new int[3][3];
    
        for (int i = 0; i < result.length; i++) {
            for (int j = 0; j < result.length; j++) {
                final int x = i;
                final int y = j;
                
                tasks.add(Executors.callable(new Runnable() {
                    @Override
                    public void run() {
                        for (int k = 0; k < a[x].length; k++) {
                            result[x][y] += a[x][k] * b[k][y];
                        }
                    }
                }));
            }
        }

        try {
            exec.invokeAll(tasks);
            exec.shutdown();
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        }

        return result;
    }