Java在并发环境中SimpleDateFormat多种解决方案

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
 
public class SimpleDateFormateTest {
 
  public static void main(String[] args) {
    final DateFormat df = new SimpleDateFormat("yyyyMMdd,HHmmss");
    ExecutorService ts = Executors.newFixedThreadPool(100);
    for (;;) {
      ts.execute(new Runnable() {     
        @Override
        public void run() {
          try {
           //生成随机数，格式化日期
           String format = df.format(new Date(Math.abs(new Random().nextLong())));
           System.out.println(format);
          } catch (Exception e) {
            e.printStackTrace();
            System.exit(1);
          }
        }
      });
    }
  }  
}

public static String formatDate(Date date)throws ParseException{
 SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 return sdf.format(date);
}

private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

public static String formatDate(Date date)throws ParseException{
 synchronized(sdf){
  return sdf.format(date);
 } 
}

 private static ThreadLocal<DateFormat> threadLocal = new ThreadLocal<DateFormat>() {
  @Override
  protected DateFormat initialValue() {
    return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  }
};

public static String format(Date date) {
  return threadLocal.get().format(date);
}