时间格式生成序列【主键】

public class GenerateSequenceUtil {

/** .log */
//    private static final Logger logger = Logger.getLogger(GenerateSequenceUtil.class);

/** The FieldPosition. */
private static final FieldPosition HELPER_POSITION = new FieldPosition(0);

/** This Format for format the data to special format. */
private final static Format dateFormat = new SimpleDateFormat("MMddHHmmssS");

/** This Format for format the number to special format. */
private final static NumberFormat numberFormat = new DecimalFormat("0000");

/** This int is the sequence number ,the default value is 0. */
private static int seq = 0;

private static final int MAX = 9999;

/**
* 时间格式生成序列
* @return String
*/
public static synchronized String generateSequenceNo() {

Calendar rightNow = Calendar.getInstance();

StringBuffer sb = new StringBuffer();

dateFormat.format(rightNow.getTime(), sb, HELPER_POSITION);

numberFormat.format(seq, sb, HELPER_POSITION);

if (seq == MAX) {
seq = 0;
} else {
seq++;
}

//        logger.info("THE SQUENCE IS :" + sb.toString());

return sb.toString();
}
public static void main(String[] args) {
System.out.println(GenerateSequenceUtil.generateSequenceNo());
}
}