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Thread: Cannot get to compile

  1. #1
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    Default Cannot get to compile

    import javax.swing.*;
    public class Circle {
     
        public double showRadius;
        public Circle (double showRadius){
                input=showRadius;
        }
        public void main(String[] args) {
            double myRadius = Double.parseDouble(JOptionPane.showInputDialog("Enter first integer"));
            double myDiameter;
            double myArea;
            calcRadius(1);
            calcRadius(myRadius);
            calcArea(1);
            calcArea(myRadius);
            calcDiameter(1);
            calcDiameter(myRadius);
     
     
        }
        public void calcRadius (double myRadius){
            double newRadius;
            newRadius = Double.parseDouble(JOptionPane.showInputDialog("Enter Radius"));
     
        }
        public void calcDiameter (double myRadius){
            double newDiameter;
            newDiameter = showRadius * 2;
     
        }
        public void calcArea (double myRadius){
            double newArea;
            newArea = 2 * myRadius * 3.14;
        }
    The error that I am receiving is:

    C:\Users\Michael\Documents\NetBeansProjects\Circle \src\circle\Circle.java:6: cannot find symbol
    symbol : variable input
    location: class Circle
    input=showRadius;

    I am new to this whole thing, and I have no clue how to fix that.

    PS: Yes, I know I'm bad at coding Java.
    Last edited by copeg; April 19th, 2011 at 12:09 PM.


  2. #2
    Administrator copeg's Avatar
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    Default Re: Cannot get to compile

    For future reference, please use the code tags. The error refers to the constructor of Circle - where is the variable input defined?

  3. #3
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    Default Re: Cannot get to compile

    A) My apologies, good sir. Thank you for your help.

    I re-watched this tutorial and... alright, I re-worked it a little.

    import javax.swing.*;
    public class Circle {
     
        public double showRadius;
        public Circle (double showRadius){
                showRadius=input;
        }
        public void main(String[] args) {
            double input = Double.parseDouble(JOptionPane.showInputDialog("Enter Radius"));
            double myDiameter;
            double myArea;  
            calcRadius(1);
            calcRadius(input);
            calcArea(1);
            calcArea(input);
            calcDiameter(1);
            calcDiameter(input);
     
     
        }
        public void calcRadius (double input){
            double newRadius;
            newRadius = Double.parseDouble(JOptionPane.showInputDialog("Enter Radius"));
     
        }
        public void calcDiameter (double input){
            double newDiameter;
            newDiameter = showRadius * 2;
     
        }
        public void calcArea (double input){
            double newArea;
            newArea = 2 * input * 3.14;
        }
    }

    Isn't the variable input now defined within the method?

  4. #4
    Administrator copeg's Avatar
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    Default Re: Cannot get to compile

    Isn't the variable input now defined within the method?
    No. Every has what is called a scope. For example, variables declared outside a method cannot by seen by the method (with a few exceptions such as the case where the variable is passed to the method or they are class instance variables). In the case of the constructor
    public double showRadius;
        public Circle (double showRadius){
                showRadius=input;//what is input?
        }
    Input is nowhere to be found...however
    public double showRadius;
        public Circle (double input){
                showRadius=input;//now input has been passed, is within scope and can be used
        }
    input is passed to the method, and is now within scope. Think about if from the computer's standpoint - look at a single method knowing nothing about the other methods - what can that method see with regards to variables?

  5. #5
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    Default Re: Cannot get to compile

    - I have change that, and now it says there are no classes.
    - I'm guessing it can just see input? I'm not exactly sure. I'm a... noob.

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