CODEWITHSUNDEEP
javaarraysindexoutofboundsexception
user2802785
user2802785

Reputation: 109

Homework Java Array

The assignment calls for a user to input 3 radius and 3 height entries which I am to gather in an array and then determine the volume for each. I am stuck on the array. For some reason I get an ArrayIndexOutOfBoundsException.

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
(CylinderTest.java:19)

I get the error at the last (6th, or height of the third entry). I don't understand what I'm doing wrong. I am having difficulty understanding the logic, is my biggest problem.

Here is the CylinderTest (main)

import javax.swing.*;

//Driver class
public class CylinderTest
{

    public static void main(String[] args)
    {

        Cylinder[] volume = new Cylinder[3];

        for (int counter = 0; counter < 6; counter++)
        {
            double radius = Double.parseDouble(JOptionPane
                    .showInputDialog("Enter the radius"));
            double height = Double.parseDouble(JOptionPane
                    .showInputDialog("Enter the height"));
            volume[counter++] = new Cylinder(radius, height);
        }

        String display = "Radius\tHeight\n";
        for (Cylinder i : volume)
        {
            if (i != null)
                display += i.toString() + "\n";
        }
        JOptionPane.showMessageDialog(null, display);
    }
}

and here is the Cylinder class

public class Cylinder
{
    // variables
    public static final double PI = 3.14159;
    private double radius, height, volume;

    // constructor
    public Cylinder(double radius, double height)
    {
        this.radius = radius;
        this.height = height;
    }

    // default constructor
    public Cylinder()
    {this(0, 0);}

    // accessors and mutators (getters and setters)
    public double getRadius()
    {return radius;}

    public void setRadius(double radius)
    {this.radius = radius;}

    public double getHeight()
    {return height;}

    public void setHeight(double height)
    {this.height = height;}

    public double getVolume()
    {return volume;}

    public void setVolume(double volume)
    {this.volume = volume;}

    // Volume method to compute the volume of the cylinder
    public double volume()
    {return PI * radius * radius * height;}

    public String toString()
    {return volume + "\t" + radius + "\t" + height; }

}

Upvotes: 2

Views: 501

Answers (5)

user2577405
user2577405

Reputation: 85

Are you sure with this?

    Cylinder[] volume = new Cylinder[3]; 

    for (int counter = 0; counter < 6; counter++)
    {
        double radius = Double.parseDouble(JOptionPane
                .showInputDialog("Enter the radius"));
        double height = Double.parseDouble(JOptionPane
                .showInputDialog("Enter the height"));
        volume[counter++] = new Cylinder(radius, height); 
        //counter will count up to 5 (Array out of Bounds exception for sure..)
        //also: why are you incrementing counter by yourself?
    }

Upvotes: -1

nhgrif
nhgrif

Reputation: 62062

Your Cylinder array has only 3 elements. Cylinder[] volume = new Cylinder[3];

Your for loop is trying to access elements after element 2 within this array. Those elements do not exist.

Upvotes: 2

blackpanther
blackpanther

Reputation: 11486

First of all, your array has been declared with a size of three. But, in your for loop, you access at the very least 6 elements of the array. So you will have increase the size of your array to at least 6. And you should change the code:

volume[counter++] = new Cylinder(radius, height);

To

volume[counter] = new Cylinder(radius, height);

Upvotes: 1

porfiriopartida
porfiriopartida

Reputation: 1556

You are declaring a 3 size array of Cylinder and you are trying to read the 6 of them.

Cylinder[] volume = new Cylinder[3]; // 3 size array

        for (int counter = 0; counter < 6; counter++) // loop 6 times
        {
            double radius = Double.parseDouble(JOptionPane
                    .showInputDialog("Enter the radius"));
            double height = Double.parseDouble(JOptionPane
                    .showInputDialog("Enter the height"));
            volume[counter++] = new Cylinder(radius, height); // read 0, 1, 2, 3, 4, 5...
        }

That should be:

Cylinder[] volume = new Cylinder[3]; // 3 size array

        for (int counter = 0; counter < volume.length; counter++) // loop 6 times
        {
            double radius = Double.parseDouble(JOptionPane
                    .showInputDialog("Enter the radius"));
            double height = Double.parseDouble(JOptionPane
                    .showInputDialog("Enter the height"));
            volume[counter] = new Cylinder(radius, height);
        }

Note the volume.length instead of 6 and the ++ removed in volume[counter++]

Upvotes: 1

Simon Forsberg
Simon Forsberg

Reputation: 13351

Your array has size 3, determined by this line:

Cylinder[] volume = new Cylinder[3];

Then you loop from 0 to 5 here:

for (int counter = 0; counter < 6; counter++)

And then you try to access one of those indexes here:

volume[counter++] = new Cylinder(radius, height);

As the array has length 3, it only has indexes 0, 1 and 2. And yet you try to access indexes higher than two.

As a side note, I suggest you change the statement to volume[counter] = new Cylinder(radius, height); otherwise you are increasing the for-loop variable counter twice in each iteration.

A good practice when looping through indexes in an array is to use the array's length in the condition:

for (int counter = 0; counter < volume.length; counter++)

This will make sure that it only iterates through the indexes that exist in the array, no matter how big or small it is.

Upvotes: 1

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