Question

When testing runtime, I use System.nanotime() in the following way:

startTime = System.nanotime();

// some statements

System.out.println("Runtime: " + (System.nanoTime() - startTime));

Is there a way to reuse this test model for other blocks of code in my programs? In other words, can I create this as a method and pass other methods to it during testing?

Answer 1

Yes, you can, but it’s even more complicated than your approach:

time(new Runnable() {
    public void run() {
        System.out.println("statements");
    }
});

static void time(Runnable r) {
    long startTime = System.nanoTime();
    r.run();
    System.out.println("Runtime: " + (System.nanoTime() - startTime));
}

In Java 7, this will get a bit simpler (I left out the ‘Measure’ implementation):

try (Measure m = new Measure()) {
    System.out.println("statements");
}

By the way, it’s better to use System.nanoTime() than System.currentTimeMillis(), not only because the former is more accurate, but also because the later will hickup around summertime change (or other system time changes).