该作业要求用户输入 3 个半径和 3 个高度条目,我将收集到一个数组中,然后确定每个条目的体积。我被困在阵列上。出于某种原因,我得到了一个ArrayIndexOutOfBoundsException
.
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
(CylinderTest.java:19)
我在最后一个(第 6 个或第三个条目的高度)收到错误。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。
这是气缸测试(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 = "RadiustHeightn";
for (Cylinder i : volume)
{
if (i != null)
display += i.toString() + "n";
}
JOptionPane.showMessageDialog(null, display);
}
}
这是圆柱类
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; }
}
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。 这些元素不存在。
的大小为 3,由以下行确定:
Cylinder[] volume = new Cylinder[3];
然后你在这里从 0 循环到 5:
for (int counter = 0; counter < 6; counter++)
然后您尝试在此处访问其中一个索引:
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,您尝试访问大于 2 的索引。
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。
循环访问数组中的索引时,一个好的做法是在以下条件下使用数组的长度:
for (int counter = 0; counter < volume.length; counter++)
这将确保它只遍历数组中存在的索引,无论它有多大或多小。
您正在声明一个 3 大小的圆柱体数组,并且您正在尝试读取其中的 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...
}
那应该是:
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);
}
注意 volume.length 而不是 6,并且 value [counter++] 中删除了 ++
首先,您的数组已声明为三大小。但是,在 for 循环中,您至少访问数组的 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);
自
volume[counter] = new Cylinder(radius, height);
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?
}