Question

I have an interactive java program which takes input from user…now i need to redirect whatever output that has been printed on the screen to a file? Is is possible.

From the java docs I got the method “System.setOut(PrintStream ps);” but i am not getting as to how to use this method?

E.g. I have a program as:

public class A{
  int i;
   void func()
   {
      System.out.println("Enter a value:");
      Scanner in1=new Scanner(System.in);
      i= in1.nextInt();
      System.out.println("i="+i);
   }
 }

Now i want to redirect the output given below to a file:

 Enter a value:
 1
 i=1

Answer 1

You can do something like:

System.setOut(new PrintStream(new BufferedOutputStream(new FileOutputStream("output.txt"))));

To write something to a file there a number of ways, you can take a look at Reading, Writing, and Creating Files tutorial.

In your case, if you would like to print exactly what is on the screen in a file too, even the user input, you can do something like:

void func(){                                                                                             
  try {                                                                                                  
    PrintStream out=new PrintStream(new BufferedOutputStream(new FileOutputStream("output.txt")));       
    System.out.println("Enter a value:");                                                                
    out.println("Enter a value:");                                                                       
    Scanner in1=new Scanner(System.in);                                                                  
    int i= in1.nextInt();                                                                                
    out.println(i);                                                                                      
    System.out.println("i="+i);                                                                          
    out.println("i="+i);                                                                                 
    out.close();                                                                                         
  } catch (FileNotFoundException e) {                                                                    
    System.err.println("An error has occurred "+e.getMessage());                                         
    e.printStackTrace();                                                                                 
  }
}