一段小代码报错，我找不到原因

[zuodicat]

如下，红色段是后面加入的，刚开始时运行正确，然后加入红色段后就报错了
package xiao.java5;
import java.io.*;
public class arrObject {
public static void main(String[] args) throws Exception{
//定义一个可以存放四只狗的对象数组
Dog dogs[]=new Dog[4];

//给狗组中的元素赋值
//dogs[0]=new Dog();
//dogs[0].setName("001");
//dogs[0].setWeight(5);

//从控制台输入各狗信息
InputStreamReader isr=new InputStreamReader(System.in);
BufferedReader br=new BufferedReader(isr);
for(int i=0;i<4;i++)
{
dogs[i]=new Dog();
System.out.println("请输入第"+(i+1)+"只狗名");
//从控制台读取狗名
String name=br.readLine();
//将名字赋给对象
dogs[i].setName(name);
System.out.println("请输入体重");
String wweight=br.readLine();
//把String->float
float weight=Float.parseFloat(wweight);
//将体重赋给对象
dogs[i].setWeight(weight);
}
//总体重
float BigDog=0;
for(int i=0;i<4;i++)
{
BigDog+=dogs[i].getWeight();
}
//计算平均体重
float avgWeight=BigDog/4;
System.out.println("平均体重是"+avgWeight+"kg");

//找出体重最大狗
//假设第一只体重最大
float maxWeight=dogs[0].getWeight();
int maxIndex=0;
//按顺序和后面的狗比较
for(int i=1;i<4;i++)

{
if(maxWeight<dogs[i].getWeight())
{
//修改
maxWeight=dogs[i].getWeight();
maxIndex=i;

}
}
System.out.println("体重最大的是第"+(maxIndex+1)+"只狗"+
"体重是"+dogs[maxIndex].getWeight());
}

//定义一个狗类
class Dog
{
private String name;
private float weight;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getWeight() {
return weight;
}
public void setWeight(float weight) {
this.weight = weight;
}
}

报错如下

[hechuanchuan]

图片挂了

[风尘中国]

你Dog类的存放位置有问题，你之前的方式相当于内部类，放在外面就行了
还有注意Java类的命名规范，首字母大写

import java.io.*;

public class ArrObject {
    public static void main(String[] args) throws Exception{
//定义一个可以存放四只狗的对象数组
        Dog dogs[]=new Dog[4];

//给狗组中的元素赋值
//dogs[0]=new Dog();
//dogs[0].setName("001");
//dogs[0].setWeight(5);

//从控制台输入各狗信息
        InputStreamReader isr=new InputStreamReader(System.in);
        BufferedReader br=new BufferedReader(isr);
        for(int i=0;i<4;i++)
        {
            dogs[i]=new Dog();
            System.out.println("请输入第"+(i+1)+"只狗名");
//从控制台读取狗名
            String name=br.readLine();
//将名字赋给对象
            dogs[i].setName(name);
            System.out.println("请输入体重");
            String wweight=br.readLine();
//把String->float
            float weight=Float.parseFloat(wweight);
//将体重赋给对象
            dogs[i].setWeight(weight);
        }
//总体重
        float BigDog=0;
        for(int i=0;i<4;i++)
        {
            BigDog+=dogs[i].getWeight();
        }
//计算平均体重
        float avgWeight=BigDog/4;
        System.out.println("平均体重是"+avgWeight+"kg");

//找出体重最大狗
//假设第一只体重最大
        float maxWeight=dogs[0].getWeight();
        int maxIndex=0;
        //按顺序和后面的狗比较
        for(int i=1;i<4;i++)

        {
            if(maxWeight<dogs[i].getWeight())
            {
                //修改
                maxWeight=dogs[i].getWeight();
                maxIndex=i;

            }
        }
        System.out.println("体重最大的是第"+(maxIndex+1)+"只狗"+
                "体重是"+dogs[maxIndex].getWeight());
    }

    //定义一个狗类

}

class Dog{
    private String name;
    private float weight;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public float getWeight() {
        return weight;
    }
    public void setWeight(float weight) {
        this.weight = weight;
    }
}

[看着奢扣]

for循环里这么写有问题
dogs[i]=new Dog();
你必须先new Test的对象
dogs[i]=new Test().new Dog();

[看着奢扣]

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;


public class Test {
	public static void main(String[] args) throws Exception{
		//定义一个可以存放四只狗的对象数组
		Dog[] dogs=new Dog[4];
		//给狗组中的元素赋值
		//dogs[0]=new Dog();
		//dogs[0].setName("001");
		//dogs[0].setWeight(5);

		//从控制台输入各狗信息
		InputStreamReader isr=new InputStreamReader(System.in);
		BufferedReader br=new BufferedReader(isr);
		for(int i=0;i<4;i++)
		{ 
			dogs[i]=new Test().new Dog();
			System.out.println("请输入第"+(i+1)+"只狗名");
			//从控制台读取狗名
			String name=br.readLine();
			//将名字赋给对象
			dogs[i].setName(name);
			System.out.println("请输入体重");
			String wweight=br.readLine();
			//把String->float
			float weight=Float.parseFloat(wweight);
			//将体重赋给对象
			dogs[i].setWeight(weight);
		}
		//总体重
		float BigDog=0;
		for(int i=0;i<4;i++)
		{
		BigDog+=dogs[i].getWeight();
		}
		//计算平均体重
		float avgWeight=BigDog/4;
		System.out.println("平均体重是"+avgWeight+"kg");

		//找出体重最大狗
		//假设第一只体重最大
		float maxWeight=dogs[0].getWeight();
		  int maxIndex=0;
		  //按顺序和后面的狗比较
		  for(int i=1;i<4;i++)
		 
		  {
		  if(maxWeight<dogs[i].getWeight())
		  {
		  //修改
		  maxWeight=dogs[i].getWeight();
		  maxIndex=i;
		 
		  }
		  }
		  System.out.println("体重最大的是第"+(maxIndex+1)+"只狗"+
		  "体重是"+dogs[maxIndex].getWeight());
		}

		//定义一个狗类
		class Dog
		{
		private String name;
		private float weight;
		public String getName() {
		return name;
		}
		public void setName(String name) {
		this.name = name;
		}
		public float getWeight() {
		return weight;
		}
		public void setWeight(float weight) {
		this.weight = weight;
		}
		}
}

[zuodicat]

[Quote=引用 2 楼 的回复:]
你Dog类的存放位置有问题，你之前的方式相当于内部类，放在外面就行了
还有注意Java类的命名规范，首字母大写

Java code


import java.io.*;

public class ArrObject {
public static void main(String[] args) throws Exception{
//定义一个可以存放四只狗的对象……
[/Quote]
谢谢

[zuodicat]

[Quote=引用 4 楼 的回复:]
Java code

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;


public class Test {
pub……
[/Quote]
谢谢

[shizhusz110]

dogs可能没有那么多 造成索引超界

[yangezheyue]

dog是一个内部类，不能直接引用的你得new一个Test之后调用它本身的dog

[yijiulove]

可以吧dog类改成静态内部类就可以了，上面的方法也可以。

package com.cd.apps;

import java.io.*;

public class Tst2 {
	public static void main(String[] args) throws Exception {
		// 定义一个可以存放四只狗的对象数组
		Dog dogs[] = new Dog[4];

		// 给狗组中的元素赋值
		// dogs[0]=new Dog();
		// dogs[0].setName("001");
		// dogs[0].setWeight(5);

		// 从控制台输入各狗信息
		InputStreamReader isr = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(isr);
		for (int i = 0; i < 4; i++) {
			dogs[i] = new Dog();
			System.out.println("请输入第" + (i + 1) + "只狗名");
			// 从控制台读取狗名
			String name = br.readLine();
			// 将名字赋给对象
			dogs[i].setName(name);
			System.out.println("请输入体重");
			String wweight = br.readLine();
			// 把String->float
			float weight = Float.parseFloat(wweight);
			// 将体重赋给对象
			dogs[i].setWeight(weight);
		}
		// 总体重
		float BigDog = 0;
		for (int i = 0; i < 4; i++) {
			BigDog += dogs[i].getWeight();
		}
		// 计算平均体重
		float avgWeight = BigDog / 4;
		System.out.println("平均体重是" + avgWeight + "kg");

		// 找出体重最大狗
		// 假设第一只体重最大
		float maxWeight = dogs[0].getWeight();
		int maxIndex = 0;
		// 按顺序和后面的狗比较
		for (int i = 1; i < 4; i++)

		{
			if (maxWeight < dogs[i].getWeight()) {
				// 修改
				maxWeight = dogs[i].getWeight();
				maxIndex = i;

			}
		}
		System.out.println("体重最大的是第" + (maxIndex + 1) + "只狗" + "体重是"
				+ dogs[maxIndex].getWeight());
	}

	// 定义一个狗类
	static class Dog {
		private String name;
		private float weight;

		public String getName() {
			return name;
		}

		public void setName(String name) {
			this.name = name;
		}

		public float getWeight() {
			return weight;
		}

		public void setWeight(float weight) {
			this.weight = weight;
		}
	}
}

[yijiulove]

 // 定义一个狗类
    static class Dog {

上面的编辑有问题，只要在class Dog 前加上static修饰就可以了。

[看着奢扣]

[Quote=引用 6 楼 的回复:]

引用 4 楼 的回复:
Java code

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;


public class ……
[/Quote]
结贴吧。