[Java]一个简易的生成流水号的类

无聊的时候写了一个简易的生成流水号的类生成的格式大致如下:

XXyyMMdd0001

import java.text.Format;

import java.text.SimpleDateFormat;

import java.util.Date;

import java.util.HashMap;

import java.util.Map;



/**

 * 

 * @author Phonnie

 *

 */

public class SerialNumber {

	

	private static final int MAX_VALUE=9999;

	private static final String FORMAT = "yyMMdd";

	private static final Format DF= new SimpleDateFormat(FORMAT);

	private static final byte[] lock = new byte[0];

	private String prefix = null;

	private Date date = null;

	private int number=1;

	private static Map<String, SerialNumber> map = new HashMap<String, SerialNumber>();

	

	private SerialNumber(String prefix,Date date){

		this.prefix = prefix;

		this.date = date;

	}

	

	public static SerialNumber newInstance(String prefix){

		Date date = new Date();

		return newInstance(prefix,date);

	} 

	

	public static SerialNumber newInstance(String prefix,Date date){

		SerialNumber o = null;

		synchronized (lock) {

			String key = getKey(prefix, date);

			if(map.containsKey(key)){

				o = map.get(key);

				int number = o.getNumber();

				if(number<MAX_VALUE){

					o.setNumber(number+1);

				}else {

					o.setNumber(1);

				}

				

			} else {

				 o = new SerialNumber(prefix,date);

				 map.put(key, o);

			}

		}

		return o;

	}

	

	

	

	private static String getKey(String prefix,Date date){

		return prefix+format(date);

	}



	private static String format(Date date){

		return DF.format(date);

	}

	

	public String toString(){

		return  prefix+ format(date) + String.format("%04d", number);

	}



	public void setNumber(int number) {

		this.number = number;

	}



	public int getNumber() {

		return number;

	}

}