简单的java问题，但是运行时就出错了。该如何解决

import java.util.Scanner;

public class NewClass {

  public static void main(String args[]) {
  NewClass application = new NewClass();
  System.out.println("How many students do you want to input?");
  Scanner str = new Scanner(System.in);
  int n = str.nextInt();
  Student[] student = new Student[n];
  application.init(student);
  application.sort(student);
  application.output(student);
  }

  public class Student {

  public String number;
  public String name;
  public int scores;

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

  public void init(Student[] student) {
  System.out.println("Please input " + student.length + " students' number,name and scores");
  Scanner string = new Scanner(System.in);
  for (int i = 0; i < student.length; i++) {
  student[i].number = string.nextLine();
  student[i].name = string.nextLine();
  student[i].scores = string.nextInt();
  }
  }

  public void sort(Student[] student) {

  Student temp = new Student("3", "enen", 3);
  for (int i = 0; i < student.length - 1; i++) {
  for (int j = 1; j < student.length; j++) {
  if (student[i].scores < student[j].scores) {
  temp = student[i];
  student[i] = student[j];
  student[j] = temp;
  }
  }
  }

  }

  public void output(Student[] student) {
  for (int i = 0; i < student.length; i++) {
  System.out.println(student[i].name);
  }
  }
}


------解决方案--------------------

Java code

import java.util.Scanner;

public class NewClass {

    public static void main(String args[]) {
        NewClass application = new NewClass();
        System.out.println("How many students do you want to input?");
        Scanner str = new Scanner(System.in);
        int n = str.nextInt();
        Student[] student = new Student[n]; // 只是初始化了数组，说明数组能放多少个Student对象，里面的每个Student对象还没有生成
        application.init(student);
        application.sort(student);
        application.output(student);
    }

    public class Student {

        public String number;
        public String name;
        public int scores;

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

    public void init(Student[] student) {
        System.out.println("Input format: number, name, scores");
        System.out.println("Please input " + student.length + " students' number,name and scores");
        Scanner string = new Scanner(System.in);

        for (int i = 0; i < student.length; i++) {
            String str = string.nextLine();
            String[] fields = str.split(",\\s*");
            System.out.println(fields);

            Student s = new Student(fields[0], fields[1], Integer.parseInt(fields[2])); // 生成Student对象
            student[i] = s;
        }
    }

    public void sort(Student