我创建了2个java文件：XCompanyShortlist.java和StudentDemo.java。 XCompanyShortlist.java包含主要方法和所有用户输入，如学生注册号，姓名，学期，GPA，CGPA，分支名称，安置状态和实习状态。
StudentDemo.java有一个超类StudentDemo初始化Reg。 No.，Name，Semester，GPA，CGPA使用参数化构造函数，它还包含一个显示所有信息的方法display（）。
类BranchStudent扩展了StudentDemo类，并包含一个名为BranchName的额外String。该类还包含一个display（）方法，该方法调用超类中的display（）方法并打印BranchName。另一个类StudentPlacement包含InternshipStatus，PlacementStatus和首选公司列表数组的变量。
这是StudentDemo.java文件代码：
class StudentDemo {
long RegNo;
String fname;
short sem;
float gpa;
float cgpa;
StudentDemo() {
RegNo = 0;
fname = "";
sem = 0;
gpa = (float) 0.0;
cgpa = (float)0.0;
}
StudentDemo(long RegNo, String fname, short sem, float gpa, float cgpa) {
this.RegNo = RegNo;
this.fname = fname;
this.sem = sem;
this.gpa = gpa;
this.cgpa = cgpa;
}
StudentDemo(StudentDemo obj) {
RegNo = obj.RegNo;
fname = obj.fname;
sem = obj.sem;
gpa = obj.gpa;
cgpa = obj.cgpa;
}
void display() {
System.out.println("------------------------------------------");
System.out.println("Registration No. :"+RegNo);
System.out.println("Full Name: "+fname);
System.out.println("Semester: "+sem);
System.out.println("GPA: "+gpa);
System.out.println("CGPA: "+cgpa);
System.out.println("------------------------------------------");
}
}
class BranchStudent extends StudentDemo {
public String BranchName;
BranchStudent(long RegNo,String fname,short sem,float gpa,float cgpa,String BranchName) {
super(RegNo,fname,sem,gpa,cgpa);
this.BranchName = BranchName;
}
BranchStudent() {
super();
BranchName = "CSE";
}
BranchStudent(BranchStudent obj) {
super(obj);
BranchName = obj.BranchName;
}
void display() {
super.display();
System.out.println("Student Branch: "+BranchName);
}
}
class StudentPlacement extends BranchStudent {
String compList[];
int StatusPlacement, StatusIntern;
StudentPlacement() {
super();
StatusPlacement = 0;
StatusIntern = 0;
compList = new String[3];
}
StudentPlacement(StudentPlacement obj) {
super(obj);
StatusPlacement = obj.StatusPlacement;
StatusIntern = obj.StatusIntern;
compList = obj.compList;
}
StudentPlacement(long RegNo, String fname, short sem, float gpa, float cgpa, String BranchName,String compList[], int StatusPlacement,int StatusIntern) {
super(RegNo, fname, sem, gpa, cgpa, BranchName);
this.compList = compList;
this.StatusPlacement = StatusPlacement;
this.StatusIntern = StatusIntern;
}
}
这是XCompanyShortlist.java文件代码：
import java.util.Scanner;
public class XCompanyShortlist {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Please Enter The Number Of Students: ");
int n = sc.nextInt();
StudentPlacement obj[] = new StudentPlacement[n];
for(int i = 0; i < n; i++) {
obj[i] = new StudentPlacement();
}
System.out.println("Please Enter The Student Details: ");
for(int i = 0; i < n; i++) {
System.out.print("Please Enter The Reg. No. :");
long RegNo = sc.nextLong();
sc.nextLine();
System.out.print("Please Enter The Full Name: ");
String fname = sc.nextLine();
System.out.print("Please Enter The Semester: ");
short sem = sc.nextShort();
System.out.print("Please Enter The GPA: ");
float gpa = sc.nextFloat();
System.out.print("Please Enter The CGPA: ");
float cgpa = sc.nextFloat();
System.out.print("Please Enter Branch Name:");
String branchName = sc.nextLine();
sc.nextLine();
System.out.println("Please Enter 3 Preferred Choice: ");
String compList[] = new String[3];
for(int x = 0; x < 3; x++) {
compList[x] = sc.nextLine();
}
System.out.print("Please Enter The Status Of Placement(0/1): ");
int statusPlacement = sc.nextInt();
System.out.print("Please Enter Status Of Internship(0/1): ");
int statusIntern = sc.nextInt();
obj[i] = new StudentPlacement(RegNo,fname,sem,gpa,cgpa,branchName,compList,statusPlacement,statusIntern);
System.out.println();
}
for(int i = 0; i < n; i++) {
obj[i].display();
}
sc.close();
}
}
我面临的问题是StudentDemo超类中的所有学生详细信息都被显示，但子类BranchStudent没有打印BranchName。我无法在代码中找到问题。
输出：
Please Enter The Number Of Students:
1
Please Enter The Student Details:
Please Enter The Reg. No. :159101046
Please Enter The Full Name: Bitan Basak
Please Enter The Semester: 3
Please Enter The GPA: 8.86
Please Enter The CGPA: 8.64
Please Enter Branch Name:CSE
Please Enter 3 Preferred Choice:
HP
Dell
Microsoft
Please Enter The Status Of Placement(0/1): 0
Please Enter Status Of Internship(0/1): 0
------------------------------------------
Registration No. :159101046
Full Name: Bitan Basak
Semester: 3
GPA: 8.86
CGPA: 8.64
------------------------------------------
Student Branch:
这是我的程序给出的输出。如您所见，学生分部未被打印。我无法理解为什么。
答案 0 :(得分：3)
据我所知，这个问题与继承无关，而是你向构造函数提供一个空行。
这意味着使用Scanner.nextLine()方法有问题。如果我将您的代码更改为：
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Please Enter The Number Of Students: ");
int n = sc.nextInt();
StudentPlacement obj[] = new StudentPlacement[n];
for(int i = 0; i < n; i++) {
obj[i] = new StudentPlacement();
}
System.out.println("Please Enter The Student Details: ");
for(int i = 0; i < n; i++) {
System.out.print("Please Enter The Reg. No. :");
long RegNo = sc.nextLong();
sc.nextLine();
System.out.print("Please Enter The Full Name: ");
String fname = sc.nextLine();
System.out.print("Please Enter The Semester: ");
short sem = sc.nextShort();
System.out.print("Please Enter The GPA: ");
float gpa = sc.nextFloat();
System.out.print("Please Enter The CGPA: ");
float cgpa = sc.nextFloat();
sc.nextLine();
System.out.print("Please Enter Branch Name:");
String branchName = sc.nextLine();
System.out.println("Please Enter 3 Preferred Choice: ");
String compList[] = new String[3];
for(int x = 0; x < 3; x++) {
compList[x] = sc.nextLine();
}
System.out.print("Please Enter The Status Of Placement(0/1): ");
int statusPlacement = sc.nextInt();
System.out.print("Please Enter Status Of Internship(0/1): ");
int statusIntern = sc.nextInt();
obj[i] = new StudentPlacement(RegNo,fname,sem,gpa,cgpa,branchName,compList,statusPlacement,statusIntern);
System.out.println();
}
for(int i = 0; i < n; i++) {
obj[i].display();
}
sc.close();
}
即。在分支名称输入之前移动sc.nextLine()，扫描程序从控制台中选择正确的值。
希望有所帮助。
问候
答案 1 :(得分：0)
在void display（）方法中你调用super display（）方法，所以super display（）方法调用的不是分支显示方法而是添加this.branchname