01/10/2018, 00:56

Lỗi Java NullPointerException

Cho em hỏi về lỗi trong Java

Đây là code của em

package SinhVien;

import java.util.Scanner;

public class SinhVien {

    private String ms;
    private String ten;
    private Date ns;
    private int soHP;
    private String[] tenHP;
    private String[] diemHP;

    public SinhVien() {
        ms = null;
        ten = "unknown";
        ns = new Date();
        soHP = 0;
        for (int i = 0; i < soHP; i++) {
            tenHP[i] = "unknown";
            diemHP[i] = "unknown";
        }
    }

    public SinhVien(String ms, String ten, Date ns, int soHP, String[] tenHP, String[] diemHP) {
        this.ms = ms;
        this.ten = ten;
        this.ns = ns;
        this.soHP = soHP;
        this.tenHP = tenHP;
        this.diemHP = diemHP;
    }

    public void nhap() {
        System.out.print("Nhap ma so sinh vien: ");
        this.ms = new Scanner(System.in).nextLine();
        System.out.print("Nhap ten sinh vien: ");
        this.ten = new Scanner(System.in).nextLine();
        System.out.println("Nhap ngay sinh sinh vien: ");
        this.ns.nhapNgay();
        System.out.print("Nhap so luong hoc phan: ");
        this.soHP = new Scanner(System.in).nextInt();
        for(int i = 0; i < soHP; i++) {
            System.out.print("Nhap ten hoc phan thu " + (i + 1) + ": ");
            this.tenHP[i] = new Scanner(System.in).nextLine();
            System.out.print("Nhap diem hoc phan thu " + (i + 1) + ": ");
            this.diemHP[i] = new Scanner(System.in).nextLine();
        }
    }

    public void xuat() {
        System.out.println("MSSV: " + this.ms);
        System.out.println("Ten SV: " + this.ten);
        System.out.println("Ngay sinh: " + this.ns.toString());
        System.out.println("So luong HP: " + this.soHP);
        for (int i = 0; i < soHP; i++) {
            System.out.println("Ten hoc phan thu " + (i + 1) + ": " + tenHP);   
            System.out.println("Diem hoc phan thu " + (i + 1) + ": " + diemHP);
        }
    }
}