WriteMessageToFile

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.text.SimpleDateFormat;
import java.util.Date;

public class WriteMessageToFile {

private String logPath;

public WriteMessageToFile(String logPath){
    this.logPath = logPath;
}

public static void main(String[] args) {
    String path = "D:\\log.log";
    String logStr = "This is a log Test!";
    new WriteMessageToFile(path).writeLogFile(logStr);
}

private synchronized void writeLogFile(String logStr) {
    if (logPath.equals("")){
     System.out.println("Error: The log path is NULL");
    }

    try {
     File file = new File(logPath);
     if (!file.exists())    //如果文件不存在,则创建一个!
      file.createNewFile();
     BufferedWriter writer = new BufferedWriter(new FileWriter(file, true));

     // Write the timestamp.
     writer.write("-----------");
     writer.newLine();
     Date nowTime = new Date();
     SimpleDateFormat time=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 
     writer.write(time.format(nowTime));
     writer.newLine();

     // Write the output message.
     writer.write(logStr);
     writer.newLine();
     writer.newLine();

     // Close file.
     writer.close();

    } catch (java.io.IOException e) {
     System.out.println("IOException:" + e.getMessage());
    }
}
}