Question

我正在尝试编写一些java代码，但我得到了一个例外。我的问题是，当我尝试添加运动员时，我得到一个空指针异常该计划是接受运动员和计算得分的平均值这是我的代码

public class AthleteTest {

        final int  MAX_ATHELETE = 200;
        private int count=0;    
        Athlete[] at = new Athlete[MAX_ATHELETE];
        Scanner sc = new Scanner(System.in);

    public void addAthletes(){
            char add = 'Y';
            while(add == 'Y'){

                System.out.println("name:");
                String name = sc.nextLine();
                at[count].setName(name);

                //Get athlete's Id number
                System.out.println("id :");
                int id = sc.nextInt();
                at.setId(id);

                //sc.nextLine();

                count++;


                System.out.println("Would you like to add another athlete?   Y / N");
                add = Character.toUpperCase(sc.next().charAt(0));
                sc.nextLine();
            }
        }
    }


    my Athlete class is as follow

    public class Athlete {

        private String name;
        private int id;

        private double [] grades;

        public Athlete(){
            this.name = null;
            this.id= 0;
        }

        public Student(String name, int id){
            this.name = name;
            this.id= id;
        }

        public String getName() {
            return name;
        }

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

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }
    }

Answer 1

您获得异常是因为您在实例化之前尝试访问运动员对象。通过这个初始化：

 Athlete[] at = new Athlete[MAX_ATHELETE];

你只是创建了一个举办运动员实例的地方。

以这种方式更改您的循环代码：

System.out.println("name:");
String name = sc.nextLine();
at[count] = new Athlete(); // Add this line
at[count].setName(name);

你应该没事。

arraylist不打印第一个元素

1 个答案: