创建文件并写入文件

Question

I created a file named 'test.txt' and then took input from the user to write the input to the file. Everything runs fine. The program doesn't show any error at all. The file is created and the program takes input from the user but when I checked the content of the file, it was empty. Can anyone figure out what is wrong with my code? The code is as follows.

package InputOutput;

import java.io.*;

public class CharacterFileReaderAndFileWriter{

private BufferedReader br = null;
private BufferedWriter bw = null;
private PrintWriter pw = new PrintWriter(System.out, true);

public File createFile() throws IOException{
    File f = new File("test.txt");
    return f;
}

public void writeToFile() throws IOException{
    try{
        bw = new BufferedWriter(new FileWriter(createFile()));
    }
    catch(FileNotFoundException ex){
        ex.printStackTrace();
    }

    //take input from the console (user)
    br = new BufferedReader(new InputStreamReader(System.in));
    String s;

    pw.println("Please enter something");
    pw.println("To stop the program, enter 'stop'");

    do{
        s = br.readLine();
        if(s.compareTo("stop")==0)
            break;
        s+= "\r\n";//adding an new line to the string s         
        bw.write(s);            
    }
    while(s.compareTo("stop")!=0);

    br.close();
    bw.close();

}

public static void main(String[] args) throws IOException{

    CharacterFileReaderAndFileWriter cfr = new CharacterFileReaderAndFileWriter();
    cfr.writeToFile();
}

}

Answer 1

Most example programs show that you have to call .flush() on your BufferedWriter before the .close() . This should not be required, .close() should call .flush() automatically, but it doesn't hurt. Also you should call all the Stream / Writer objects .close() methods in reverse order as well, again correctly written classes should call .close() on all the object they wrap, but it doesn't hurt to do it anyway.

Other things that might catch you out later:

if(s.compareTo("stop")==0)

should be

if ("stop".equalsIgnoreCase(s))

it is more efficient, eliminates the possibility of a NullPointerException on s , handles any case of stop and most importantly more idiomatic Java than using .compareTo()

    s+= "\r\n";//adding an new line to the string s         
    bw.write(s);        

should be

    bw.write(System.getProperty("line.separator"));        
    bw.write(s);        

The s+= creates intermediate objects and garbage that needs to be collected. Hard coding line endings is bad as well.

Answer 2

You need close the outputstream. file.close();