Simple program question

[Chris Reech]

Below is some very simple code for finding the diameter, circumference, and area of a circle with a radius inputed by the user. Can someone please tell me why it is not running?

Thanks!

  import java.io.*;                       // Package for stream readers
  public class Circle
 {
  public static void main(String[] args)
 {
  final double PI = 3.14159;              // Value for PI  
  double radius;                          // Radius of Circle
  double diameter;                        // Diameter of a Circle
  double circumference;                   // Circumference of a Circle
  double area;                            // Area of a Circle
 
  BufferedReader in;                      // Input stream for strings
  in = new BufferedReader(new InputStreamReader(System.in));
  // Prompt for Radius
  System.out.print("Enter Radius " );
  radius = in.readLine();                 // Get radius
 
  diameter = (radius * 2.0);              // Calculates diameter
  circumference = (2.0 * PI * radius);    // Calculates circumference
  area = (PI * radius * radius);          // Calculates area
 
  // Output Result
  System.out.println("Diameter = " + diameter);
  System.out.println("Circumference = " + circumference);
  System.out.println("Area = " + area);
 }
  }

[ October 17, 2006: Message edited by: Chris Reech ]

[ October 17, 2006: Message edited by: Chris Reech ]
[ October 17, 2006: Message edited by: Chris Reech ]

[Chetan Parekh]

Originally posted by Chris Reech:
radius = in.readLine(); // Get radius

Replace above code with following code

radius = Double.parseDouble( in.readLine()); // Get radius

Beucase the in.readLine() return String, while radius is a double.

Aslo you need to add try/catch block surrounding your code.
[ October 17, 2006: Message edited by: Chetan Parekh ]

[art gems]

One way is to replace your radius= line with:

radius = Double.parseDouble(in.readLine());

Also, since you're changing a String to Double here, you have to 'try-catch' or 'throws'.

praseDouble method should be used sparingly.

[Chris Reech]

Originally posted by Chetan Parekh:


Replace above code with following code

radius = Double.parseDouble( in.readLine()); // Get radius

Beucase the in.readLine() return String, while radius is a double.

Aslo you need to add try/catch block surrounding your code.

[ October 17, 2006: Message edited by: Chetan Parekh ]

Now I got this message

[Bauke Scholtz]

Nothing to do with the problem, but it might be interesting to know that you can set Pi as follows:

final double PI = Math.PI;

[Chetan Parekh]

Chris Reech, Add try/catch block in your code - as I mentioned before.

Check how to do that below

public static void main(String[] args) {
try { 
 
[B]//Put all your code here[/B]

} catch(Exception e) {
System.out.println(e);
}
}

[ October 18, 2006: Message edited by: Chetan Parekh ]

[Chris Reech]

Originally posted by Chetan Parekh:
Chris Reech, Add try/catch block in your code - as I mentioned before.

Check how to do that below

public static void main(String[] args) {
try { 
 
[B]//Put all your code here[/B]

} catch(Exception e) {
System.out.println(e);
}
}

[ October 18, 2006: Message edited by: Chetan Parekh ]

Excellent, it worked! 2 more things:

I am very novice so please bear with me. How do you assign the radius to a float variable? Also, I need to drop .0 from the diameter value and shorten the decimal places to 3. Shown below.

Thanks!

[Justin Fox]

look into, NumberFormat/DeciamlFormat classes

[Jesper de Jong]

Or use System.out.printf(...) instead of System.out.println(...) to print the output. With printf, you can specify the format that you want for the numbers. Look it up in the API documentation (you can find printf(...) in the class java.io.PrintStream).

Example:

System.out.printf("Diameter = %.3f", diameter);