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

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  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

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