Java 简单Project 2, 学生数据库

任务描述

实现：

package com.company;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        // ask how many students we want to add
        System.out.println("how many students you would like to add?\n");
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        Student[] students = new Student[n];

        // Create a number of new students
        for(int i=0;i<n;i++){
            students[i]=new Student();
            students[i].enroll();
            students[i].payTuition();
        }

        for(int i=0;i<n;i++){
            System.out.println(students[i].toString());
        }
    }
}

package com.company;

import java.util.Scanner;

public class Student {
    private String firstName;
    private String lastName;
    private int gradeYear;
    private String studentID;
    private String courses="";
    private int tuitionBalance = 0;
    private static int costOfCourse = 600;
    private static int id = 1000;

    //Constructor: prompt user to enter student's name and year
    public Student(){
        Scanner in = new Scanner(System.in);
        System.out.print("Enter student first name: ");
        this.firstName = in.nextLine();

        System.out.print("Enter student last name: ");
        this.lastName = in.nextLine();

        System.out.print("Enter student class level:\n1-Freshmen\n2-Sophomore\n3-Junior\n4-Senior\n");
        this.gradeYear = in.nextInt();

        setStudentID();

    }
    //Generate ID
    private void setStudentID(){
        //Grade Level + ID
        id++;
        this.studentID = gradeYear + "" +id;
    }

    //Enroll in courses
    public void enroll(){
        //get inside a loop, user hits 0 to exit
        do{
            System.out.println("Enter a course to enroll (Q to quit): ");
            Scanner in = new Scanner(System.in);
            String course = in.nextLine();
            if(!course.equals("Q")){ //this is important
                courses = courses + "\n" + course;
                tuitionBalance = tuitionBalance+costOfCourse;
            }
            else{
                System.out.println("BREAK\n");
                break;
            }
        }while (true);
    }

    //View balance
    public void viewBalance(){
        System.out.println("Your balance is: $"+tuitionBalance);
    }
    //Pay tuition
    public void payTuition(){
        viewBalance();
        System.out.println("Enter your payment: ");
        Scanner in = new Scanner(System.in);
        int payment = in.nextInt();
        tuitionBalance = tuitionBalance - payment;
        System.out.println("Thank you for payment of $ "+payment);
        viewBalance();
    }

    //Show status
    public String toString(){
        return "Name: "+firstName+" "+lastName+"Grade Level: "+gradeYear+
                "StudentID: "+ studentID+
                "\nCourses Enrolled: "+ courses +
                "\nBalance: "+ tuitionBalance;
    }
}

运行结果

注意：

在比较String, Char 等类型时，不要想当然用 == 符号。

if(!course.equals("Q")){ //this is important