直接上程式碼：

package com.inspur.log;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintWriter;
import java.util.Calendar;

public class WriteLog {

	 private static WriteLog instance = null;
	 private WriteLog(){};
	 public static WriteLog getInstance() {
        if( instance == null ) {
            instance = new WriteLog();
        }
        return instance;
    }
	 public void logger(String fileNameHead,String logString) {
	   try {
	    String logFilePathName=null;
	    Calendar cd = Calendar.getInstance();//日誌檔案時間
	    int year=cd.get(Calendar.YEAR);
	    String month=addZero(cd.get(Calendar.MONTH)+1);
	    String day=addZero(cd.get(Calendar.DAY_OF_MONTH));
	    String hour=addZero(cd.get(Calendar.HOUR_OF_DAY));
	    String min=addZero(cd.get(Calendar.MINUTE));
	    String sec=addZero(cd.get(Calendar.SECOND));
	   
	   
	    File fileParentDir=new File("./log");<span style="font-family: Arial, Helvetica, sans-serif;">//判斷log目錄是否存在
</span>	    if (!fileParentDir.exists()) {
	     fileParentDir.mkdir();
	    }
	    if (fileNameHead==null||fileNameHead.equals("")) {
	     logFilePathName="./log/"+year+month+day+hour+".log";//日誌檔名
	    }else {
	     logFilePathName="./log/"+fileNameHead+year+month+day+hour+".log";//日誌檔名
	    }
	   
	    PrintWriter printWriter=new PrintWriter(new FileOutputStream(logFilePathName, true));
	    String time="["+year+month+day+"-"+hour+":"+min+":"+sec+"] ";
	    printWriter.println(time+logString);
	    printWriter.flush();
	   
	   } catch (FileNotFoundException e) {
	    // TODO Auto-generated catch block
	    e.getMessage();
	   }
	}
	 

/**整數小於10前面補0
* @param i
* @return
*/
	public static String addZero(int i) {
	   if (i<10) {
	    String tmpString="0"+i;
	    return tmpString;
	   }
	   else {
	    return String.valueOf(i);
	   }  
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		WriteLog log = null;
		log.getInstance().logger("test", "hello world, t02,test");
	}

}