使用java如何实现异步将日志写到文件中

package com.tydic.ESUtil;  import java.io.File; import java.io.FileWriter; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Properties;  public class LogWriter { // 日志的配置文件   public static final String LOG_CONFIGFILE_NAME = "log.properties";   // 日志文件名在配置文件中的标签   public static final String LOGFILE_TAG_NAME = "logfile";      // 默认的日志文件的路径和文件名称   private final String DEFAULT_LOG_FILE_NAME = "./logtext.log";   // 该类的唯一的实例   private static LogWriter logWriter;   // 文件输出流   private PrintWriter writer;    // 日志文件名   private String logFileName;       private LogWriter() throws LogException{     this.init();   }   private LogWriter(String fileName) throws LogException{     this.logFileName = fileName;     this.init();   }      public synchronized static LogWriter getLogWriter()throws LogException{     if (logWriter == null){       logWriter = new LogWriter();     }     return logWriter;   }   public synchronized static LogWriter getLogWriter(String logFileName)throws LogException{     if (logWriter == null){       logWriter = new LogWriter(logFileName);     }     return logWriter;   }       public synchronized void log(String logMsg) {     this.writer.println(new java.util.Date() + ": " + logMsg);   }      public synchronized void log(Exception ex) {     writer.println(new java.util.Date() + ": ");     ex.printStackTrace(writer);   }       private void init() throws LogException{     //如果用户没有在参数中指定日志文件名，则从配置文件中获取。     if (this.logFileName == null){       this.logFileName = this.getLogFileNameFromConfigFile();       //如果配置文件不存在或者也没有指定日志文件名，则用默认的日志文件名。       if (this.logFileName == null){         this.logFileName = DEFAULT_LOG_FILE_NAME;       }     }     File logFile = new File(this.logFileName);     try {       // 其中的FileWriter()中的第二个参数的含义是:是否在文件中追加内容       // PrintWriter()中的第二个参数的含义是：自动将数据flush到文件中       writer = new PrintWriter(new FileWriter(logFile, true), true);       System.out.println("日志文件的位置：" + logFile.getAbsolutePath());     } catch (IOException ex) {       String errmsg = "无法打开日志文件:" + logFile.getAbsolutePath();       // System.out.println(errmsg);       throw new LogException(errmsg, ex);     }   }      private String getLogFileNameFromConfigFile() {      try {        Properties pro = new Properties();        //在类的当前位置,查找属性配置文件log.properties        InputStream fin = getClass().getResourceAsStream(LOG_CONFIGFILE_NAME);        if (fin != null){         pro.load(fin);//载入配置文件         fin.close();          return pro.getProperty(LOGFILE_TAG_NAME);       } else {         System.err.println("无法打开属性配置文件: log.properties" );        }     }catch (IOException ex) {        System.err.println("无法打开属性配置文件: log.properties" );      }     return null;   }   //关闭LogWriter   public void close() {     logWriter = null;     if (writer != null){       writer.close();     }   }    public static void main(String[] args) {     LogWriter logger = null;     try {       String fileName = "d:/temp/logger.log";       logger = LogWriter.getLogWriter(fileName); //     logger.log("First log!"); //     logger.log("第二个日志信息"); //     logger.log("Third log"); //     logger.log("第四个日志信息");       String content="tableaA|device_number|13701010";       StringBuffer sb=new StringBuffer();       for(int i=0;i<1000000;i++){         sb.append(content).append(i).append(";\n");       }       content=sb.toString();       long startTime=System.currentTimeMillis();       logger.log(content);       long endTime=System.currentTimeMillis();       System.out.println("总消耗时间："+(endTime-startTime));       logger.close(); //     ReadFromFile.readFileByLines(fileName);     } catch (LogException e) {       e.printStackTrace();     }   } }