根据时间生成流水号

package test;

import java.text.SimpleDateFormat;
import java.util.Date;
/**
* 获取主键:返回17位时间戳+3位递增数(同一时间递增)
*/
public class IdCreator {
private static int addPart = 1;
private static String result = "";
private static SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmssSSS");
private static String lastDate = "";
/**
* 获取主键
* @param length 长度
* @return 返回17位时间戳+3位递增数
*/
public synchronized static String getId(int length) {
//获取时间部分字符串
Date now = new Date();
String nowStr = sdf.format(now);

//获取数字后缀值部分
if (IdCreator.lastDate.equals(nowStr)) {
addPart += 1;
} else {
addPart = 1;
lastDate = nowStr;
}

if (length > 17) {
length -= 17;
for (int i = 0; i < length - ((addPart + "").length()); i++) {
nowStr += "0";
}
nowStr += addPart;
result = nowStr;
} else {
result = nowStr;
}
return result;
}

public static void main(String[] args) {
System.out.println(IdCreator.getId(20));
}
}