所以我想首先告诉您我正在自学 Java,你们是我最接近老师的人。非常感谢你容忍我这个简单而明显的问题。我只是想学习。我又一次遇到了一个我一生都无法弄清楚的错误。
这里是错误:
Exception in thread "main" java.lang.NullPointerException
at Advisor_score.All_user.Score1(All_user.java:13)
at Advisor_score.All_user.main(All_user.java:28)
这是我的评级类代码:
package Advisor_score;
public class Rating {
double [] Ratings;
double sum=0;
double raw_advisor;
double advisor_score;
public Rating (double [] x){
Ratings = x;
}
public double Score(){
for(int i=2;i<Ratings.length;i++){
sum+=Ratings[i];
}
raw_advisor=((sum-(3*(Ratings.length-2)))/4);
advisor_score= 2.5+(2.5*(1-Math.pow(Math.E, -.5*raw_advisor)));
return advisor_score;
}
这是我的另一个类的代码:
package Advisor_score;
public class All_user{
double [] ADVISOR_SCORE;
Rating [] All_users;
double score;
public All_user(Rating...args){
All_users=args;
}
public double [] Score1(){
for (int j = 0;j<All_users.length;j++){
score=All_users[j].Score();
ADVISOR_SCORE[j]=score;
}
return ADVISOR_SCORE;
}
public void print(){
for(int i = 0;i<ADVISOR_SCORE.length;i++){
System.out.println(ADVISOR_SCORE[i]);
}
}
public static void main(String[] args){
double p1_1[] = {101,1,5,5,5};
double p2_1[] = {101,1,1,2,3};
Rating d = new Rating(p1_1);
Rating e = new Rating(p2_1);
All_user all=new All_user(d, e);
all.Score1();
all.print();
}
}
再次感谢 StackOverflow 的各位。您的帮助非常宝贵!!
最佳答案
您尚未初始化 ADVISOR_SCORE 和 All_users 数组,但您确实尝试分配值并使用它们。当你声明
double[] ADVISOR_SCORE; // this is null until assigned
在某些时候,它需要被赋值
ADVISOR_SCORE = new double[size];
关于java - Java中面向对象编程的问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3710986/