Using a While Loop in Java

Question

import java.io.*;
import java.util.*;

    public class volumeConeD

{//class
    public static void main (String [] args)
        {//main
            Scanner keyBoard = new Scanner(System.in);//input for keyBoard
        //variables
    double volume;
    double radius;
    double hieght;
    double oneThird = 0.3333;
    double pie = 3.14;
    double yes = 1.0;
    boolean r = true;

try
    {//begin of try
    while(r == true){
    System.out.print("Volume of a Cone... V=1/3(3.14)r^2(h)");
    System.out.println ();
    System.out.println ();

    radius = getRadius(radius);//call to method
    radius = keyBoard.nextDouble ();
System.out.print("Enter a Height      ");
hieght = keyBoard.nextDouble ();
            //math
        volume = oneThird * pie * radius * radius * hieght;
        System.out.printf ("Volume =       " + volume);
                                }//end of try                                           

            catch (Exception Error){
            System.out.println("You entered wrong data");
            }
            System.out.println ();
        System.out.print("Does the user wish to try again?");
        System.out.println ();
        System.out.print("Enter 1 to go again OR any other key to end.");
        yes = keyBoard.nextDouble();
        }//end of while


}//end of main
public static double getRadius(double mRadius)
{
    System.out.print("Enter Radius Squared Number      ");

return mRadius; 
    }
}//end of program

this is my first time posting on this forum, so please excuse how ask...here goes... all i am trying to do with this is repeat this problem under user control using a sentinel method(while loop). I had it almost working earlier but i kept getting errors about how i defined "r". Now i get errors about my catch try blocks. please help.

volumeConeD.java:35: error: 'catch' without 'try'
            catch (Exception Error){
            ^
volumeConeD.java:35: error: ')' expected
            catch (Exception Error){
                            ^
volumeConeD.java:35: error: not a statement
            catch (Exception Error){
                  ^
volumeConeD.java:35: error: ';' expected
            catch (Exception Error){
                                  ^
volumeConeD.java:19: error: 'try' without 'catch', 'finally' or resource declarations
try
^
5

I see it says 'catch' without 'try' so I started counting your brackets after the first appearance of try keyword, there is 2 opening brackets and one closing bracket with comment // end of try. So your catch is inside the try I guess. — Leonardo
– Leonardo, Commented Sep 6, 2013 at 21:54
If you would clean up your intention you would probably spot the issue yourself. — Janick Bernet
– Janick Bernet, Commented Sep 6, 2013 at 21:55
Out of scope: a class name begins with an uppercase letter in Java. — C.Champagne
– C.Champagne, Commented Sep 6, 2013 at 22:22

rgettman · Accepted Answer · 2013-09-06 21:55:16Z

1

You placed your try { outside the while loop, but the corresponding catch is within the while loop. But must be either outside the loop or inside the loop, together.

Try placing the try { lines inside the while loop.

Additionally, it looks like these lines won't work either:

radius = getRadius(radius);//call to method
radius = keyBoard.nextDouble ();

All getRadius does is print out a prompt and return the passed in parameter, radius. But radius hasn't been initialized yet. But it looks like nothing is done with it yet anyway. Rename the method something like promptForRadius, and it doesn't need to take in a parameter or return anything.

public static void promptForRadius()
{
    System.out.print("Enter Radius Squared Number      ");
}

Then when calling it:

promptForRadius();
// Then you can call this line (unchanged)
radius = keyBoard.nextDouble();

answered Sep 6, 2013 at 21:55

rgettman

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2 Comments

user2755775 Over a year ago

i did that but now it says...volumeConeD.java:27: error: variable radius might not have been initialized radius = getRadius(radius); //call to method

user2755775 Over a year ago

Thank You So Much rgettman. it worked! i truly appreciate it.

Leonardo · Accepted Answer · 2013-09-06 21:57:10Z

0

Where your comment says // end of try it should really say // end of while and vice versa.

answered Sep 6, 2013 at 21:57

Leonardo

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Comments

Chandra · Accepted Answer · 2013-09-06 22:01:23Z

I have reformatted the code. Braces for try/catch block cannot end before while loop braces. Also you have to initialize variables before using them (e.g,. radius). Eclipse like IDE will be helpful to format and identify compilation errors. BTW I have not checked the logical correctness of the code but more of compilations and syntax issues

import java.util.Scanner;

public class volumeConeD

{
    public static void main(String[] args)
    {
        Scanner keyBoard = new Scanner(System.in);// input for keyBoard
        // variables
        double volume;
        double radius = 0.0;
        double hieght;
        double oneThird = 0.3333;
        double pie = 3.14;
        double yes = 1.0;
        boolean r = true;

        try
        {// begin of try
            while (r == true)
            {
                System.out.print("Volume of a Cone... V=1/3(3.14)r^2(h)");
                System.out.println();
                System.out.println();

                radius = getRadius(radius);// call to method
                radius = keyBoard.nextDouble();
                System.out.print("Enter a Height      ");
                hieght = keyBoard.nextDouble();
                // math
                volume = oneThird * pie * radius * radius * hieght;
                System.out.printf("Volume =       " + volume);

                System.out.println();
                System.out.print("Does the user wish to try again?");
                System.out.println();
                System.out.print("Enter 1 to go again OR any other key to end.");
                yes = keyBoard.nextDouble();
            }// end of while

        }// end of try

        catch (Exception Error)
        {
            System.out.println("You entered wrong data");
        }
    }// end of main

    public static double getRadius(double mRadius)
    {
        System.out.print("Enter Radius Squared Number      ");

        return mRadius;
    }
}// end of program

DwB · Accepted Answer · 2013-09-06 22:13:48Z

This seems to be your problem

try
{
    while (...)
    {
       int blammo;

       try
       {
           ... code
           blammo = 9;
       }
       catch ...
       {
          // catching here means that the while loop will continue looping.
       }

       System.out.println("Blammo: " + blammo); // This results in the error: variable
       // blammo might not have been initialized.   This is because the assignment
       // "blammo = 9" is inside the try block and if an exception was thrown before
       // the assignment then it (the assignment)  will never execute and blammo will
       // be uninitialized.

    } // end of while loop

} // end of outter try
catch ...
{
   // catching here means that the exception exits the while loop.
}

Junior Dussouillez · Accepted Answer · 2013-09-06 22:21:38Z

You use a catch, but it's not matching with the try... oneThird variable can be set as 1 / 3 (more precision). Same for PI, the Math library already has a PI definition. The function getRadius is useless, you should take it off, or maybe replace it by a function which asks the user to enter a double number.

import java.util.Scanner;

public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double volume, radius, height, oneThird = (1.0 / 3);
        int continueExecution = 1;

        try {
            while (continueExecution == 1) { // same as r == true (redundant)
                System.out.println("Volume of a Cone... V=1/3(3.14)r^2(h)\n\n"); // '\n' is the newline character
                radius = getDoubleValue(sc, "Enter radius : ");
                height = getDoubleValue(sc, "Enter height : ");
                volume = oneThird * Math.PI * Math.pow(radius, 2) * height;
                System.out.println("Volume = " + volume + "\nEnter 1 to start again, or another number to exit: ");
                continueExecution = sc.nextInt();
            }
        } catch (Exception e) { // Pokemon exception handling !
            System.err.println(e.getMessage());
        }
    }

    public static double getDoubleValue(Scanner sc, String msg) {
        System.out.print(msg);
        return sc.nextDouble();
    }

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