Write or redirect console output to a file & again reset to standard output in java

1. In java application, we write to console output using System.out.print*.
2. We would like to redirect console output to a file. (Stream output -> File)
   • e.g. System.out.println(“1. Console output written to file”) should written to a file.
   • Stream written to console output will be redirected to a file.
3. We will demonstrate to reset the console output (Opposite of Step 2 – Stream output -> Standard output).
   • We will redirect the stream to standard output instead of a file.
   • We will reset the standard output, so that stream output will be redirected to Standard console output.
4. System class has setOut method to set the stream output.
   • static void setOut(PrintStream out)
     Reassigns the “standard” output stream.

1. Write console output to a file & reset back to standard output in java

package org.learn;

import java.io.FileDescriptor;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintStream;


public class WriteConsoleOutputToFile {

    public static void main(String[] args)  throws FileNotFoundException {
        writeConsoleOutputToFile();
    }
    private static void writeConsoleOutputToFile() throws FileNotFoundException {

        System.out.println("1. String written to console");
        System.out.println("2. Another String written to console");

        PrintStream printStream = new PrintStream("ConsoleOutputFile.txt");
        System.setOut(printStream);

        System.out.println("1. Console output written to file");
        System.out.print("2. Another console output written to file");
        System.out.printf("\n3. Write yet another string to file");

        //Redirect to console output
        PrintStream consoleStream = new PrintStream(
                                    new FileOutputStream(FileDescriptor.out));
        System.setOut(consoleStream);
        System.out.println("3. Reset to write on console output");
        System.out.println("4. Demonstration of console output");

    }
}

2. O/P: Contents written to a “ConsoleOutputFile.txt” file

• “ConsoleOutputFile.txt” file will be generated in the current working directory.
• The contents written to a file is as follows:

• 1. Console output written to file
  2. Another console output written to file
  3. Write yet another string to file

3. O/P:  Content written to standard console in java

1. String written to console
2. Another String written to console
3. Reset to write on console output
4. Demonstration of console output