/* From: "COMPUTATIONAL PHYSICS, 2nd Ed" 
   by RH Landau, MJ Paez, and CC Bordeianu 
   Copyright Wiley-VCH, 2007.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2007;
   MJ Paez, Univ Antioquia, 2007; and CC Bordeianu, Univ Bucharest, 2007.
   Support by National Science Foundation                              
*/
//  AFileIO.java:  Area with File I/O 

import java.io.*;                               // Import I/O library

public class AFileIO {
  public static final double PI = 3.141593;              // Constants
  
	public static void main(String[] argv) throws 
    IOException, FileNotFoundException {           // Main with throw
			
    double r, A;                                 // Declare variables
                               // Ask user to prepare input from file
    System.out.println("Enter name and r in Name.dat"); 
    BufferedReader b = new BufferedReader(new InputStreamReader(
	                   new FileInputStream("Name.dat")));  // Open file
    System.out.println("Hi "+b.readLine());   // Read, print 1st line
    String s = b.readLine();         // Read 2nd line, convert double
    r = Double.valueOf(s).doubleValue();          // String to double
    System.out.println("r = "+r);
    A = PI * r * r;                                 // Do computation
    System.out.println("Done, look in A.dat");        // Screen print
    PrintWriter q=new PrintWriter(new FileOutputStream("A.dat"),true);
    q.println("r = " +r);                              // File output
    q.println("A = "+A);   
  }
}