Question

I am trying to get the output of my java program to write to a file.

The user inputs some data which should not be included in the file. When the program responds it should output information to the user, as well as write SOLELY the output to a file.

From examples I have begun with this at the top of my driver class:

static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
static String lineFromOutput;

This code is in every place where I might receive output from the program:

try {
    lineFromInput = in.readLine();
    FileWrite.write(lineFromInput);
} catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
}

And the class its calling is:

public class FileWrite {
    public static void write(String message) { 
        PrintWriter out = null;
        try {
            out = new PrintWriter(new FileWriter("output.txt"), true);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        out.write(message);
        out.close();
    }
}

It creates the output file, but thats it. None of the output from the program is written.
I’ve looked over numerous examples and this seems to be the easiest way to get the ball rolling, although I’m open to any other suggestions.

Thanks!

Answer 1

I think it should be InputStremReader with single t in statement below:

static BufferedReader in= new BufferedReader(new OutputtStreamReader(System.in));
static String lineFromOutput;

As

static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
static String lineFromOutput;

EDIT: This works fine. Please make sure you provide the input through input console. Also please note that it reads and write(overwrite) single line ONLY.

    public class FileWrite {
       public static void write(String message) { 
                PrintWriter out = null;
              try {
                  out = new PrintWriter(new FileWriter("output.txt"), true);
              } catch (IOException e) {
                  // TODO Auto-generated catch block
                  e.printStackTrace();
              }
                out.write(message);
                out.close();
        }

       public static void main(String[] args){
           String lineFromInput;
           try {
                BufferedReader in = new BufferedReader(
                                            new InputStreamReader(System.in));
                lineFromInput = in.readLine();
                FileWrite.write(lineFromInput);
                in.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
           }
       }
     }

EDIT 2: Updated program for multi-line inputs. Its not best way to open and close file each time to write, but I am just trying to make your program work with minor changes. Let me know, if you need suggestion to avoid repeated opening/closing of the output file.

Change Highlights:

1. Read lines until “exit”(change the word as desired) is received in input

2. Open the file in append mode.

   public class FileWrite {
      public static void write(String message) { 
               PrintWriter out = null;
             try {
                 out = new PrintWriter(new FileWriter("output.txt", true), true);
             } catch (IOException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
               out.write(message);
               out.close();
       }
   
      public static void main(String[] args){
          String lineFromInput = "";
          try {
               System.out.println("Provide the inputs in any number of lines");
               System.out.println("Type \"exit\" in new line when done");
               BufferedReader in = new BufferedReader(
                                   new InputStreamReader(System.in));
               while(!"exit".equals(lineFromInput)){
                  lineFromInput = in.readLine();
                  FileWrite.write(lineFromInput+System.lineSeparator());
               }
               in.close();
           } catch (IOException e) {
               // TODO Auto-generated catch block
               e.printStackTrace();
          }
      }
    }
   

EDIT3: Your updated program using Scanner to read the inputs:

        private static HashMap<Integer, Object> shapes = 
                                              new HashMap<Integer, Object>();
        static int i = 0;

        public static void main(String[] args) {
            PrintWriter output = null;
            Scanner scanner = new Scanner(System.in);
            try {
                output = new PrintWriter(new FileWriter("output.txt"), true);
            } catch (IOException e1) {
                System.err.println("You don't have accress to this file");
                System.exit(1);
            }
            String command = "";
            while(!"quit".equalsIgnoreCase(command)){
                System.out.println("Enter your Command: ");
                command = scanner.next();
                if (command.equalsIgnoreCase("create")) {
                    String type = scanner.next();
                    if (type.equalsIgnoreCase("line")) {
                        double length = scanner.nextDouble();
                        Line l = new Line(length);
                        scanner.nextLine();//flush the previous line
                        String line = scanner.nextLine();
                        output.format("%s", line);
                        shapes.put(i, l);
                        i++;
                    }else if (type.equalsIgnoreCase("circle")) {
                        double radius = scanner.nextDouble();
                        String color = scanner.next();
                        Circle c = new Circle(radius, Colors.valueOf(color));
                        scanner.nextLine();//flush the previous line
                        String line = scanner.nextLine();
                        output.format("%s", line);
                        shapes.put(i, c);
                        i++;
                    }else if (type.equals("rectangle")) {
                        double length = scanner.nextDouble();
                        double width = scanner.nextDouble();
                        String color = scanner.next();
                        Rectangle r = new Rectangle(length, width,
                        Colors.valueOf(color));
                        scanner.nextLine();//flush the previous line
                        String line = scanner.nextLine();
                        output.format("%s", line);
                        shapes.put(i, r);
                        i++;
                    }else if (type.equals("square")) {
                        double length = scanner.nextDouble();
                        String color = scanner.next();
                        Square s = new Square(length, Colors.valueOf(color));
                        scanner.nextLine();//flush the previous line
                        String line = scanner.nextLine();
                        output.format("%s", line);
                        shapes.put(i, s);
                        i++;
                    }
                }else if (command.equals("printbyperimeter")) {
                    Shape[] shapeArray = shapes.values().toArray(new Shape[0]);
                    Arrays.sort(shapeArray);
                            System.out.println("Print in ascending order...");
                    for (int j = 0; j < shapeArray.length; j++) {
                        Shape temp = shapeArray[j];
                        if (temp.getClass().getName().equals("Line")) {
                            System.out.println("Shape: " 
                                    + temp.getClass().getName() + ", Perimeter: "
                                    + temp.getPerimeter());
                                } else {
                            System.out.println("Shape: " 
                                    + temp.getClass().getName() + ", Color: "
                                    + ((Colorable) temp).getColor()
                                    + ", Perimeter: " + temp.getPerimeter());
                                }
                            }
                }else if (command.equals("printbyarea")) {
                    Shape[] shapeArray = shapes.values().toArray(new Shape[0]);
                    System.out.println("Print in random order...");
                    for (int j = 0; j < shapeArray.length; j++) {
                        Shape temp = shapeArray[j];
                        if (!temp.getClass().getName().equals("Line")) {
                            System.out.println("Shape: "
                                    + temp.getClass().getName() + ", Color: "
                                    + ((Colorable) temp).getColor() + ", Area: "
                                    + ((Areable) temp).getArea());
                                }
                        }
                }else if (command.equals("quit")) {
                    scanner.close();
                    System.exit(0);
                }
           }
           output.close();
        }