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Thread: when i run applet

  1. #1
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    Default when i run applet

    when i run applet my radius is 0 why? heres my code



    import java.awt.Graphics;
    import javax.swing.JApplet;
    import javax.swing.JOptionPane;

    public class Assign3 extends JApplet
    {
    private double diameter;
    private double circum;
    private double area;
    private double pi = Math.PI;
    private double radius;

    public void init()
    {
    String radius = JOptionPane.showInputDialog(
    "Enter the radius of the circle" );

    double radius1 = Double.parseDouble( radius );
    radius = radius;
    diameter = 2*radius1;
    circum = 2*(pi*radius1);
    area = pi*(radius1*radius1);
    }
    public void paint( Graphics g )
    {
    super.paint( g );
    g.drawString( "The radius is " + radius , 25, 25);
    g.drawString( "The diameter is " + diameter , 25, 45);
    g.drawString( "The circumference is " + circum , 25, 65);
    g.drawString( "The area is " + area , 25, 85);
    }
    }


  2. #2
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    Default Re: when i run applet

    It is good practice to not declare variables with the same name as a variable with a larger scope. Consider the code below:

    private double radius;
    ...
    {
    String radius = JOptionPane.showInputDialog(
    "Enter the radius of the circle" );
     
    double radius1 = Double.parseDouble( radius );
    radius = radius;
    ...
    }

    Notice how you have a double named radius and a String named radius? Well, when you make the statement radius=radius, it is looking at the variable with the most relevant scope, which means it is looking at the radius variable that is a String. So, you are setting the String radius to be equal to the String radius.

    You also probably meant to set radius equal to radius1.

    So, to fix this problem you have two options.
    1) Since your double radius is a class variable, you can use the this.variable declaration, as shown below:

    private double radius;
    ...
    {
    String radius = JOptionPane.showInputDialog(
    "Enter the radius of the circle" );
     
    double radius1 = Double.parseDouble( radius );
    this.radius = radius1;
    ...
    }

    2) You can change the name of the variable with the least scope, like shown below:
    private double radius;
    ...
    {
    String radiusString = JOptionPane.showInputDialog(
    "Enter the radius of the circle" );
     
    double radius1 = Double.parseDouble( radiusString );
    radius = radius1;
    ...
    }
    Last edited by aussiemcgr; February 22nd, 2011 at 03:54 PM.
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  3. #3
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    Default Re: when i run applet

    ahh i see this i have radius set in string and my variable therefore it goes to both.. thanks

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