计蒜客-----泥塑课

一开始不知道错在了哪里,一直报空指针错误,后来才发现是对象数组没理解好

classroom room[] = new classroom[num];

只是声明了对象数组,并未初始化,所以直接使用room[i]会报空指针错误,正确的应该如下

classroom room[] = new classroom[num];
        for (int i = 0; i < num; i++) {
            room[i] = new classroom();
        }

声明,并且初始化变量,接下来才可以使用.

完整代码如下:

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;


public class Main{
    public static void main(String[] args){
        Scanner input = new Scanner(System.in);
        List<String> children = new ArrayList<String>();
        int num;
        while(true){
            num = input.nextInt();
            if(num!=-1){
                //这里只是声明数组,还要创建对象
                classroom room[] = new classroom[num];
                for (int i = 0; i < num; i++) {
                    room[i] = new classroom();
                }
                for (int i = 0; i < num; i++) {
                    room[i].x = input.nextInt();
                    room[i].y = input.nextInt();
                    room[i].z = input.nextInt();
                    room[i].name = input.next();
                }
                children.add(judge(room));
            }else{
                break;
            }
        }
        for (String string : children) {
            System.out.println(string);
        }
    }
    public static String judge(classroom room[]){
        int avg = valuesum(room)/room.length;
        int temp1 = 0,temp2 = 0;
        for (int i = 0; i < room.length; i++) {
            if(avg > room[i].volume()){
                temp1 = i;
            }else if(avg <room[i].volume()){
                temp2 = i;
            }
        }
        String temp = room[temp2].name+" took clay from "+room[temp1].name;
        return temp;

    }
    public static  int valuesum(classroom room[]) {
        int sum = 0;
        for (int i = 0; i < room.length; i++) {
            sum = sum + room[i].volume();
        }
        return sum;
    }
}
class classroom{
    int x = 0;
    int y = 0;
    int z = 0;
    String name = "";
    public int volume() {
        return x*y*z;

    }
}

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