Thread.start()

Examples

Two threads each compute their own part:

void main() throws InterruptedException {
    long[] sums = new long[2];
    Thread a = new Thread(() -> { for (int i = 1; i <= 500; i++) sums[0] += i; });
    Thread b = new Thread(() -> { for (int i = 501; i <= 1000; i++) sums[1] += i; });
    a.start();
    b.start();
    a.join();
    b.join();
    IO.println(sums[0] + sums[1]);
}

Output:

500500

Notes

Calling run() instead of start() is a common mistake: the code runs in the current thread with no parallelism. The same Thread object cannot be started twice — IllegalThreadStateException. The order in which threads run is not defined, so wait for them with join() before using their results.