如何使用BufferedWriter写入标准输出

Question

I am currently writing an application that produces several log files using BufferedWriter. While debugging, however, I want to write to System.out instead of a file. I figured I could change from:

log = new BufferedWriter(new FileWriter(tokenizerLog));

to:

BufferedWriter log = new BufferedWriter(new OutputStreamWriter(System.out));
log.write("Log output\n");

as opposed to:

System.out.println("log output")

The new OutputStreamWriter option has not been working though. How do I change just the Object inside the BufferedWriter constructor to redirect from a file to Standard out. Because I have several log files I will be writing to, using System.out everywhere and changing the output to a file isn't really an option.

Answer 1

Your approach does work, you are just forgetting to flush the output:

try {    
  BufferedWriter log = new BufferedWriter(new OutputStreamWriter(System.out));

  log.write("This will be printed on stdout!\n");
  log.flush();
}
catch (Exception e) {
  e.printStackTrace();
}

The both OutputStreamWriter and PrintWriter are Writer instances so you can just do something like:

BufferedWriter log;

Writer openForFile(String fileName) {
  if (fileName != null)
    return new PrintWriter(fileName);
  else
    return new OutputStreamWriter(System.out);
}

log = new BufferedWriter(openForFile(null)); //stdout
log = new BufferedWriter(openForFile("mylog.log")); // using a file

or whatever, it is just to give you the idea..

Answer 2

Since you mention that this is for logging, you might want to look at using a logger library like log4j. It'll let you change the log destination (either log file or console) by making changes in configuration files only.