JAVA生成订单号(日期+流水号)

package test; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.File; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.text.DecimalFormat; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Date; import java.util.List; import java.util.concurrent.TimeUnit; public class test1 { /** * @param args */ public static void main(String[] args) throws InterruptedException { SerialNumber serial = new FileEveryDaySerialNumber(5, "EveryDaySerialNumber.dat"); while(true) { System.out.println(serial.getSerialNumber()); TimeUnit.SECONDS.sleep(60); } } } abstract class SerialNumber { public synchronized String getSerialNumber() { return process(); } protected abstract String process(); } abstract class EveryDaySerialNumber extends SerialNumber { protected final static SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd"); protected DecimalFormat df = null; public EveryDaySerialNumber(int width) { if(width < 1) { throw new IllegalArgumentException("Parameter length must be great than 1!"); } char[] chs = new char[width]; for(int i = 0; i < width; i++) { chs[i] = '0'; } df = new DecimalFormat(new String(chs)); } protected String process() { Date date = new Date(); int n = getOrUpdateNumber(date, 1); return format(date) + format(n); } protected String format(Date date) { return sdf.format(date); } protected String format(int num) { return df.format(num); } protected abstract int getOrUpdateNumber(Date current, int start); } class FileEveryDaySerialNumber extends EveryDaySerialNumber { private File file = null; private final static String FIELD_SEPARATOR = ","; public FileEveryDaySerialNumber(int width, String filename) { super(width); file = new File(filename); } @Override protected int getOrUpdateNumber(Date current, int start) { String date = format(current); int num = start; if(file.exists()) { List<String> list = FileUtil.readList(file); String[] data = list.get(0).split(FIELD_SEPARATOR); if(date.equals(data[0])) { num = Integer.parseInt(data[1]); } } FileUtil.rewrite(file, date + FIELD_SEPARATOR + (num + 1)); return num; } } class FileUtil { public static void rewrite(File file, String data) { BufferedWriter bw = null; try { bw = new BufferedWriter(new FileWriter(file)); bw.write(data); } catch (IOException e) { e.printStackTrace(); } finally { if(bw != null) { try { bw.close(); } catch(IOException e) { e.printStackTrace(); } } } } public static List<String> readList(File file) { BufferedReader br = null; List<String> data = new ArrayList<String>(); try { br = new BufferedReader(new FileReader(file)); for(String str = null; (str = br.readLine()) != null; ) { data.add(str); } } catch (IOException e) { e.printStackTrace(); } finally { if(br != null) { try { br.close(); } catch(IOException e) { e.printStackTrace(); } } } return data; } }