关于Java 获取时间戳的方法

import java.util.ArrayList;
import java.util.List;
import java.util.function.Consumer;


public class TimePerformance {


public static final int LOOP_COUNT = 9999999;
public static final int THREAD_COUNT = 30;


public static void main(String[] args) {


Runnable millisTest = () -> {


long start = System.currentTimeMillis();
for (int i = 0; i < LOOP_COUNT; i++) {
System.currentTimeMillis();
}
long end = System.currentTimeMillis();


System.out.printf("%s : %f ns per call\n",
Thread.currentThread().getName(), ((double)end - start) * 1000000 / LOOP_COUNT);
};


Runnable nanoTest = () -> {


long start = System.currentTimeMillis();
for (int i = 0; i < LOOP_COUNT; i++) {
System.nanoTime();
}
long end = System.currentTimeMillis();


System.out.printf("%s : %f ns per call\n",
Thread.currentThread().getName(), ((double)end - start) * 1000000 / LOOP_COUNT);
};


Consumer<Runnable> testing = test -> {
System.out.println("Single thread test:");
test.run();


System.out.println(THREAD_COUNT + " threads test:");
List<Thread> threads = new ArrayList<>();
for (int i = 0; i < THREAD_COUNT; i++) {
Thread t = new Thread(test);
t.start();
threads.add(t);
}
// Wait for all threads to finish
threads.forEach(thread -> {
try {
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
});
};


System.out.println(" Test System.nanoTime()");
testing.accept(nanoTest);
System.out.println(" Test System.currentTimeMillis()");
testing.accept(millisTest);
}
}