Next we promised to write a getNextInteger() method that will accept an integer from the user. Here it is:

static int getNextInteger() { String line; DataInputStream in = new DataInputStream(System.in); try { line = in.readLine(); int i = Integer.valueOf(line).intValue(); return i; } catch (Exception e) { return -1; } } // getNextInteger ends here

// Write the Fahrenheit to Celsius table in a file import java.io.*; class FahrToCelsius { public static void main (String args[]) { double fahr, celsius; double lower, upper, step; lower = 0.0; // lower limit of temperature table upper = 300.0; // upper limit of temperature table step = 20.0; // step size fahr = lower; try { FileOutputStream fout = new FileOutputStream("test.out); // now to the FileOutputStream into a PrintStream PrintStream myOutput = new PrintStream(fout); while (fahr <= upper) { // while loop begins here celsius = 5.0 * (fahr-32.0) / 9.0; myOutput.println(fahr + + celsius); fahr = fahr + step; } // while loop ends here } // try ends here catch (IOException e) { System.out.println("Error: + e); System.exit(1); } } // main ends here } There are only three things necessary to write formatted output to a file rather than to the standard output:

1. Open a FileOutputStream using a line like

   FileOutputStream fout = new FileOutputStream("test.out); This line initializes the FileOutputStream with the name of the file you want to write into.

2. Convert the FileOutputStream into a PrintStream using a statement like

   PrintStream myOutput = new PrintStream(fout); The PrintStream is passed the FileOutputStream from step 1.

3. Instead of using System.out.println() use myOutput.println() . System.out and myOutput are just different instances of the PrintStream class. To print to a different PrintStream we keep the syntax the same but change the name of the PrintStream .