我正在尝试根据用户输入创建一系列数学学生，理科学生和计算机专业学生。
所以基本上用户应该选择他们想要添加的学生，然后输入学生的详细信息。
下面我添加了我到目前为止的代码：
主Java类：
public class Lab4 {
public static final int DEBUG = 0;
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
Student s[] = new Student[10];
s[0] = new MathStudent(4,5);
s[1] = new MathStudent(5,7);
s[2] = new MathStudent(2,8);
s[3] = new MathStudent(3,6);
s[4] = new ScienceStudent(8,9);
s[5] = new ScienceStudent(3,6);
s[6] = new ScienceStudent(4,9);
s[7] = new ComputerStudent(6,12);
s[8] = new ComputerStudent(11,14);
s[9] = new ComputerStudent(13,17);
}
}
学生班：
public class Student {
private String name;
private int age;
public String gender = "na";
public static int instances = 0;
// Getters
public int getAge(){
return this.age;
}
public String getName(){
return this.name;
}
// Setters
public void setAge(int age){
this.age = age;
}
public void setName(String name){
if (Lab4.DEBUG > 3) System.out.println("In Student.setName. Name = "+ name);
this.name = name;
}
/**
* Default constructor. Populates name,age,gender,course and phone Number
* with defaults
*/
public Student(){
instances++;
this.age = 18;
this.name = "Not Set";
this.gender = "Not Set";
}
/**
* Constructor with parameters
* @param age integer
* @param name String with the name
*/
public Student(int age, String name){
this.age = age;
this.name = name;
}
/**
* Gender constructor
* @param gender
*/
public Student(String gender){
this(); // Must be the first line!
this.gender = gender;
}
/**
* Destructor
* @throws Throwable
*/
protected void finalize() throws Throwable{
//do finalization here
instances--;
super.finalize(); //not necessary if extending Object.
}
public String toString (){
return "Name: " + this.name + " Age: " + this.age + " Gender: "
+ this.gender;
}
public String getSubjects(){
return this.getSubjects();
}
}
MathStudent课程：
public class MathStudent extends Student {
private float algebraGrade;
private float calculusGrade;
public MathStudent(float algebraGrade, float calculusGrade) {
this.algebraGrade = algebraGrade;
this.calculusGrade = calculusGrade;
}
public MathStudent() {
super();
algebraGrade = 6;
calculusGrade = 4;
}
// Getters
public void setAlgebraGrade(float algebraGrade){
this.algebraGrade = algebraGrade;
}
public void setCalculusGrade(float calculusGrade){
this.calculusGrade = calculusGrade;
}
// Setters
public float getAlgebraGrade() {
return this.algebraGrade;
}
public float getCalculusGrade() {
return this.calculusGrade;
}
/**
* Display information about the subject
* @return
*/
@Override
public String getSubjects(){
return("Algebra Grade: " + algebraGrade + " Calculus Grade: "
+ calculusGrade);
}
}
scienceStudent class：
public class ScienceStudent extends Student {
private float physicsGrade;
private float astronomyGrade;
/**
* Default constructor
*/
public ScienceStudent() {
super();
physicsGrade = 6;
astronomyGrade = 7;
}
public ScienceStudent(float physicsGrade, float astronomyGrade) {
this.physicsGrade = physicsGrade;
this.astronomyGrade = astronomyGrade;
}
// Getters
public void setPhysicsGrade(float physicsGrade){
this.physicsGrade = physicsGrade;
}
public void setAstronomyGrade(float astronomyGrade){
this.astronomyGrade = astronomyGrade;
}
// Setters
public float getPhysicsGrade() {
return this.physicsGrade;
}
public float getAstronomyGrade() {
return this.astronomyGrade;
}
/**
* Display information about the subject
* @return
*/
@Override
public String getSubjects(){
return("Physics Grade: " + physicsGrade + " Astronomy Grade: "
+ astronomyGrade);
}
}
computerStudent class：
public class ComputerStudent extends Student {
private float fortanGrade;
private float adaGrade;
/**
* Default constructor
*/
public ComputerStudent() {
super();
fortanGrade = 4;
adaGrade = 9;
}
public ComputerStudent(float fortanGrade, float adaGrade) {
this.fortanGrade = fortanGrade;
this.adaGrade = adaGrade;
}
// Getters
public void setFortanGrade(float fortanGrade){
this.fortanGrade = fortanGrade;
}
public void setAdaGrade(float adaGrade){
this.adaGrade = adaGrade;
}
// Setters
public float getFortanGrade() {
return this.fortanGrade;
}
public float getAdaGrade() {
return this.adaGrade;
}
/**
* Display information about the subject
* @return
*/
@Override
public String getSubjects(){
return("Fortan Grade: " + fortanGrade + " Ada Grade: " + adaGrade);
}
}
我将如何解决这个问题？
答案 0 :(得分：0)
您可以询问每个输入上具有类型的学生数量并动态创建对象。 这是一个例子
System.out.println("Enter total number of students");
int n = scannerObject.nextInt();
Student students[] = new Students[n];
for(int i=0;i<n;i++){
int type = scannerObject.nextInt();
if(type == 1)
students[i] = new MathStudent();
}
同样，你可以为别人写作。
答案 1 :(得分：0)
允许用户输入他的选择作为输入 你可以这样做（由你的评论解释）
伪代码 -
打印：
为数学学生输入1
为理科学生输入2
为Comp学生输入3
输入选择
现在在您的代码中使用多个if else或更好的switch语句
switch(choice){
case 1: create object of math student
break;
case 2: create object of science student
break;
case 3:create object of comp student
break;
default: if not above by default do this
}
答案 2 :(得分：0)
您可以使用ArrayList和switch case来让您的生活更轻松。你的代码应该是这样的：
import java.util.ArrayList;
import java.util.Scanner;
public class Students {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
ArrayList<Student> students = new ArrayList<>();
int age;
boolean addMore = true;
String name, gender;
Student st;
while (addMore) {
System.out.print("Give lesson (Computers, Math, Science): ");
String lesson = input.nextLine();
switch (lesson) {
case "Math":
// Read student's info
System.out.print("Give student's name: ");
name = input.nextLine();
System.out.print("Give student's gender: ");
gender = input.nextLine();
System.out.print("Give student's age: ");
age = input.nextInt();
System.out.print("Give student's Algebra grade: ");
int alg = input.nextInt();
System.out.print("Give student's Calculus grade: ");
int calc = input.nextInt();
input.nextLine(); // This is needed in order to make the next input.nextLine() call work (See here: https://stackoverflow.com/questions/13102045/scanner-is-skipping-nextline-after-using-next-nextint-or-other-nextfoo )
// Create the student object and pass info
st = new MathStudent(alg, calc);
st.setName(name);
st.setAge(age);
st.gender = gender;
students.add(st); // Adding the student in the list
System.out.println(st);
System.out.println(((MathStudent) st).getSubjects());
break;
case "Science":
// Read student's info
System.out.print("Give student's name: ");
name = input.nextLine();
System.out.print("Give student's gender: ");
gender = input.nextLine();
System.out.print("Give student's age: ");
age = input.nextInt();
System.out.print("Give student's Physics grade: ");
int physics = input.nextInt();
System.out.print("Give student's Astronomy grade: ");
int astronomy = input.nextInt();
input.nextLine();// This is needed in order to make the next input.nextLine() call work (See here: https://stackoverflow.com/questions/13102045/scanner-is-skipping-nextline-after-using-next-nextint-or-other-nextfoo )
// Create the student object and pass info
st = new ScienceStudent(physics, astronomy);
st.setName(name);
st.setAge(age);
st.gender = gender;
students.add(st); // Adding the student in the list
System.out.println(st);
System.out.println(((ScienceStudent) st).getSubjects());
break;
case "Computers":
// Read student's info
System.out.print("Give student's name: ");
name = input.nextLine();
System.out.print("Give student's gender: ");
gender = input.nextLine();
System.out.print("Give student's age: ");
age = input.nextInt();
System.out.print("Give student's Fortran grade: ");
int fortran = input.nextInt();
System.out.print("Give student's Ada grade: ");
int ada = input.nextInt();
input.nextLine();// This is needed in order to make the next input.nextLine() call work (See here: https://stackoverflow.com/questions/13102045/scanner-is-skipping-nextline-after-using-next-nextint-or-other-nextfoo )
// Create the student object and pass info
st = new ComputerStudent(fortran, ada);
st.setName(name);
st.setAge(age);
st.gender = gender;
students.add(st); // Adding the student in the list
System.out.println(st);
System.out.println(((ComputerStudent) st).getSubjects());
break;
default:
System.out.println("Wrong lesson");
addMore = false;
break;
}
if (addMore) {
System.out.println("Add another student? (y/n)");
String ans = input.nextLine();
addMore = ans.equals("y");
} else {
addMore = true;
}
}
System.out.println("Students");
for (Student student : students) {
System.out.println(student);
}
}
}
上面的代码要求提供课程名称（计算机，数学，科学），如果是其中之一，则会读取有关学生的所有信息以及相应课程的成绩。它创建对象并将其添加到列表students中。当添加所有信息时，它询问用户他/她是否想要添加另一个学生，如果他写了字母y，则再次进行所有这些，直到用户回答与字母y不同的内容（大多数字母n）例）。在这之后它打印所有的学生＆＃39;信息通过itterating列表。
注意：我认为在您的ComputerStudent类的代码中，您想要命名变量fortranGrade而不是fortanGrade（在getSubjects函数中也更改它）。
链接：
我希望这有助于你。如果您有任何问题或想要更多的东西，您可以这样做。
<强>更新
下面的代码执行相同的操作，但它使用for循环而不是switch case，正如您在评论中提到的那样。
package students;
import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Lab4 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
ArrayList<Student> students = new ArrayList<>();
int age;
boolean addMore = true;
String name, gender;
Student st;
ArrayList<Class<?>> studentClasses = new ArrayList<>();
studentClasses.add(MathStudent.class);
studentClasses.add(ComputerStudent.class);
studentClasses.add(ScienceStudent.class);
while (addMore) {
System.out.print("Give lesson (Computers, Math, Science): ");
String lesson = input.nextLine();
addMore = false;
for (Class studentClass : studentClasses) {
try {
st = (Student) studentClass.newInstance();
if (st.getLessonName().equals(lesson)) {
// Read student's info
System.out.print("Give student's name: ");
name = input.nextLine();
System.out.print("Give student's gender: ");
gender = input.nextLine();
System.out.print("Give student's age: ");
age = input.nextInt();
System.out.print("Give student's " + st.getSubjectsNames()[0] + " grade: ");
float firstSubj = input.nextFloat();
System.out.print("Give student's " + st.getSubjectsNames()[1] + " grade: ");
float secondSubj = input.nextFloat();
input.nextLine(); // This is needed in order to make the next input.nextLine() call work (See here: https://stackoverflow.com/questions/13102045/scanner-is-skipping-nextline-after-using-next-nextint-or-other-nextfoo )
// Create the student object and pass info
st = (Student) studentClass.getConstructor(float.class, float.class).newInstance(firstSubj, secondSubj);
st.setName(name);
st.setAge(age);
st.gender = gender;
students.add(st); // Adding the student in the list
System.out.println(st);
System.out.println(st.getSubjects());
addMore = true;
break;
}
} catch (NoSuchMethodException | SecurityException | InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException ex) {
Logger.getLogger(Lab4.class.getName()).log(Level.SEVERE, null, ex);
}
}
if (addMore) {
System.out.println("Add another student? (y/n)");
String ans = input.nextLine();
addMore = ans.equals("y");
} else {
System.out.println("Wrong lesson. Try again.");
addMore = true;
}
}
System.out.println("Students");
for (Student student : students) {
System.out.println(student);
}
}
}
您还需要在类中添加函数，如下所述：
学生班：
public String getLessonName(){
return "";
}
public String[] getSubjectsNames(){
return new String[] {"", ""};
}
MathStudent课程：
@Override
public String[] getSubjectsNames(){
return new String[] {"Algebra", "Calculus"};
}
@Override
public String getLessonName(){
return "Math";
}
ComputerStudent类：
@Override
public String[] getSubjectsNames(){
return new String[] {"Fortran", "Ada"};
}
@Override
public String getLessonName(){
return "Computers";
}
ScienceStudent课程：
@Override
public String[] getSubjectsNames(){
return new String[] {"Physics", "Astronomy"};
}
@Override
public String getLessonName(){
return "Science";
}
更改：代码首先使用学生类（studdentClasses）创建一个arraylist，并添加当前在项目中的学生的所有课程（MathStudent， ComputerStudent，ScienceStudent）。然后用户添加课程的名称。然后（而不是切换案例）有一个for循环，它通过studdentClasses列表进行检查，并检查用户所写的课程名称是否与学生的课程相同使用getLessonName函数。之后，询问学生的所有信息和科目的成绩，以及问题（给学生的物理等级），它使用函数getSubjectsNames。所有其他事情都像以前一样。
答案 3 :(得分：-2)
你有一个主类，这本质上是你需要的，但你需要从命令行读取。太棒了，从命令行运行。一旦你跑了，注意你做了什么，你也可以在那里传递参数。一旦你传递了参数，它们就会排成一行。此行在逻辑上是可拆分的，因此将其拆分为您的代码。例如，通过一些关键词之后的一对数字，比如科学和直到下一个关键词并再次从java中提出并在你那里问一个新问题。