How to take User Input and Perform Calculations

[jo15765]

I am trying to write a Java program that will display a pop up box asking for user input (which I have learned will be a String type). Then convert the string to int and perform calculations. I am getting stuck...can someone provide some help on the calculations part (I keep getting an error that says can not find symbols?)?

int num1
int num1Doubled
int num1Tripled

		JFrame frame = new JFrame("A Dialog to Get Integer Input from the User");
		String Name = JOptionPane.showInputDialog(frame, "Enter A Random Number");
		

		num1 = Integer.parseInt(Name);


		num1Doubled = 2 * num1;
		num1Tripled = 3 * num1;

[KevinWorkman]

Is any of that inside a method? Please post an SSCCE that demonstrates exactly what you're doing.

[jo15765]

This is the code (still a work in progress) that I am working with:

import javax.swing.JOptionPane;
import java.awt.*;
import javax.swing.*;

public class ArithmaticOperations
{
    public static void main (String args[])
    {
		int num1
		int num1Doubled
		int num1Tripled
 
        JFrame frame = new JFrame("A Dialog to Get Integer Input from the User");
        String Name = JOptionPane.showInputDialog(frame, "Enter A Random Number");
         
 
        num1 = Integer.parseInt(Name);
 
 
        num1Doubled = 2 * num1;
        num1Tripled = 3 * num1;
		
		//Somehow use JOption.DisplayMessageBox to show the results in a pop-up
	}
}

And now this is the error I get:
C:\A_Programs>javac tes.java
tes.java:9: error: ';' expected
int num1
^
tes.java:10: error: ';' expected
int num1Doubled
^
tes.java:11: error: ';' expected
int num1Tripled
^
3 errors

[wdh321]

This is the code (still a work in progress) that I am working with:

And now this is the error I get:
C:\A_Programs>javac tes.java
tes.java:9: error: ';' expected
int num1
^
tes.java:10: error: ';' expected
int num1Doubled
^
tes.java:11: error: ';' expected
int num1Tripled
^
3 errors

Take a look at lines 9,10,11. Then look at where you would expect to see ";"

[jo15765]

Oh good grief! Of course it is something extremely easy that I just carelessly overlooked!

Any tips on how to use JOption.DisplayMessageBox to show the results in a pop-up? Like one pop up window but each on a seperate line show:
the userinput
numberDoubled
numberTripled

[KevinWorkman]

Oh good grief! Of course it is something extremely easy that I just carelessly overlooked!

Any tips on how to use JOption.DisplayMessageBox to show the results in a pop-up? Like one pop up window but each on a seperate line show:
the userinput
numberDoubled
numberTripled

Can you use html? Does \n work?

Recommended reading: How to Make Dialogs (The Java™ Tutorials > Creating a GUI With JFC/Swing > Using Swing Components)

[jo15765]

So try it like this:

JOptionPane.showMessageDialog(frame, The User Inputted: " + num1 \n);
JOptionPane.showMessageDialog(frame, The number Doubled: " + num1Doubled \n);
JOptionPane.showMessageDialog(frame, The number Tripled: " + num1Tripled \n);

[KevinWorkman]

So try it like this:

JOptionPane.showMessageDialog(frame, The User Inputted: " + num1 \n);
JOptionPane.showMessageDialog(frame, The number Doubled: " + num1Doubled \n);
JOptionPane.showMessageDialog(frame, The number Tripled: " + num1Tripled \n);

Huh? No, that's now what I meant at all. That will result in three dialogs, not a single dialog with three lines.

[jo15765]

How would I code it so that each one displays in the same dialog box then?

[KevinWorkman]

How would I code it so that each one displays in the same dialog box then?

You're almost there, so try experimenting with different Strings. What happens when you have the \n in the middle of a String displayed on a JOptionPane (I honestly don't know for sure it will work, but it's what I would try since it takes 3 seconds to test)? What happens if you use some html tags like br?

[wdh321]

So try it like this:

JOptionPane.showMessageDialog(frame, The User Inputted: " + num1 \n);
JOptionPane.showMessageDialog(frame, The number Doubled: " + num1Doubled \n);
JOptionPane.showMessageDialog(frame, The number Tripled: " + num1Tripled \n);

You can add these into the same dialog box as KevinWorkman said (currently you are making 3) and use the \n for new lines
BUT your code you have there wont work yet, you need to use "" around your strings currently you just have one " in the middle.

[jo15765]

Thanks for the help! It took me a quick minute but I just had to encompass the /n with quotes so my code reads like:

JOptionPane.showMessageDialog(frame, "The User Inputted: " + num1 + "\n" + "The number doubled is: " +num1Doubled + "\n" + "The number tripled is: " + num1Tripled );

[jo15765]

Actually one more question...

I tried to add one more calculation to the above code (which is working perfectly) so here is my modified code:

import javax.swing.JOptionPane;
import java.awt.*;
import javax.swing.*;
import java.lang.Math;
 
public class ArithmaticOperations
{
    public static void main (String args[])
    {
        int num1;
        int num1Doubled;
        int num1Tripled;
int numtimesP;
  
        JFrame frame = new JFrame("A Dialog to Get Integer Input from the User");
        String Name = JOptionPane.showInputDialog(frame, "Enter A Random Number");
          
  
        num1 = Integer.parseInt(Name);
  
  
        num1Doubled = 2 * num1;
        num1Tripled = 3 * num1;
        numtimesP = Math.PI * num1;
		
        //Somehow use JOption.DisplayMessageBox to show the results in a pop-up
		JOptionPane.showMessageDialog(frame, "The User Inputted: " + num1 + "\n" + "The number doubled is: " +num1Doubled + "\n" + "The number tripled is: " + num1Tripled );
    }
}

And I am getting this error:
on line 22 error: possible loss of precision
numtimesP = Math.PI * num1

required: int
found: double

What did I do wrong?

[KevinWorkman]

Your numtimesP variable is an int, which can only be whole numbers (0, 1, -5, etc). Math.PI is a double, which is a decimal. So when you store a decimal-type number in an int, you lose any information after the decimal point.

A quick google of "java possible loss of precision" gives several more detailed explanations.