Alarm Class waitUntil()

/*
     * Tests the functionality of the alarm class.
     *  Because "nachos will not function correctly with more than one alarm",
     *  and the only alarm is instantiated in the threadKernel class, the
     *  alarm is passed here from the threadKernel's selfTest.
     */
    public static void selfTest(final Alarm alarm) {
        System.out.format("\nTesting waitUntil in the Alarm class...\n");
        KThread alarmThread1 = new KThread(new Runnable() {
                public void run(){
                        System.out.format("Thread 1 waiting, 500000 ticks...\n");
                        alarm.waitUntil(500000);
                        System.out.format("\nThread 1 done waiting.\n\n");
                }
        });
        KThread alarmThread2 = new KThread(new Runnable() {
                public void run(){
                        System.out.format("Thread 2 waiting, 1000000 ticks...\n");
                        alarm.waitUntil(1000000);
                        System.out.format("Thread 2 done waiting.\n\n");
                }
        });
        KThread alarmThread3 = new KThread(new Runnable() {
                public void run(){
                        System.out.format("Thread 3 waiting, 3000000 ticks...\n");
                        alarm.waitUntil(3000000);
                        System.out.format("Thread 3 done waiting.\n\n");
                }
        });
        KThread alarmThread4 = new KThread(new Runnable() {
                public void run(){
                        System.out.format("Thread 4 waiting, 5000000 ticks...\n");
                        alarm.waitUntil(5000000);
                        System.out.format("Thread 4 done waiting.\n\n");
                }
        });

        alarmThread1.fork();
        alarmThread2.fork();
        alarmThread3.fork();
        alarmThread4.fork();
        // have to join or machine halts prematurely
        alarmThread4.join();
    }