全局唯一自增id生成

public class Bbbb {
	public static void main(String[] args) {
		//42位时间戳+8位机器码+16位hash预留
		long time = System.currentTimeMillis();
		long serverid = 100; // serverid 不能超过256
		long userid = 123213123123l;
		long last16 = getLast(userid, 16);
		System.out.println(last16);
		
		long id = (time << 24) + (serverid << 16) + last16;
		System.out.println(id);
		
		long id_last16 = getLast(id, 16);
		System.out.println(id_last16);
	}
	
	public static long getLast(long l, int last){
		long i =  (l >> last) << last;
		return l-i;
	}
}

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全局唯一自增id生成

原文：http://supben.iteye.com/blog/2257422