Question

该作业要求用户输入3个半径和3个高度的条目，我将收集到这个条目中，然后确定每个条目的音量。我被困在阵列上。出于某种原因，我得到了ArrayIndexOutOfBoundsException。

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

我在最后（第6个，或第三个条目的高度）得到错误。我不明白我做错了什么。我很难理解逻辑，这是我最大的问题。

这是CylinderTest（主要）

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);
    }
}

这里是Cylinder类

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; }

}

Answer 1

您的Cylinder数组只有3个元素。 Cylinder[] volume = new Cylinder[3];

您的for loop正在尝试访问此数组中元素2之后的元素。那些元素不存在。

Answer 2

您的数组的大小为3，由此行决定：

Cylinder[] volume = new Cylinder[3];

然后你在这里从0循环到5：

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

然后你尝试在这里访问其中一个索引：

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

由于数组的长度为3，因此它只有索引0,1和2.然而，您尝试访问的索引高于2。

作为旁注，我建议您将语句更改为volume[counter] = new Cylinder(radius, height);，否则您将在每次迭代中将for循环变量counter增加两次。

循环遍历数组中的索引时的一个好习惯是在条件中使用数组的长度：

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

这将确保它只迭代数组中存在的索引，无论它有多大或多小。

Answer 3

您正在声明一个3尺寸的Cylinder数组，而您正在尝试阅读其中的6个。

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...
        }

应该是：

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);
        }

请注意volume.length而不是6，并在卷中删除++ [counter ++]

Answer 4

首先，您的数组已声明为3。但是，在for循环中，您至少可以访问数组中的6个元素。因此，您将数组的大小增加到至少6.您应该更改代码：

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

要

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

Answer 5

你确定吗？

    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?
    }

家庭作业Java数组

5 个答案: