標籤:style blog color io java ar for 資料 div
import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;public class sequence { private static final long ONE_STEP = 10; private static final Lock LOCK = new ReentrantLock(); private static long lastTime = System.currentTimeMillis(); private static short lastCount = 0; private static int count = 0; @SuppressWarnings("finally") public static String nextId() { LOCK.lock(); try { if (lastCount == ONE_STEP) { boolean done = false; while (!done) { long now = System.currentTimeMillis(); if (now == lastTime) { try { Thread.currentThread(); Thread.sleep(1); } catch (java.lang.InterruptedException e) { } continue; } else { lastTime = now; lastCount = 0; done = true; } } } count = lastCount++; } finally { LOCK.unlock(); return lastTime+""+String.format("%03d",count); } } public static void main(String[] args) { //測試 for(int i=0;i<1000;i++) { System.out.println(nextId()); } }}
據說如果是用在叢集環境,需要在前面加上機器的編號,或者IP。
JAVA版資料庫主鍵ID產生器