java - 尝试创建一个我可以进一步操作的学生数据库

Question

我正在尝试创建一个数据库(作为 ArrayList)，用于存储学生的信息(对象数组)，但是我遇到了“addStudent()”函数的问题，因为它似乎只利用最新的通过调用函数创建的数组。我知道我可能错过了眼前的一些东西，但我已经开始过度思考，我相信并认为我需要一双新的眼睛。任何帮助是极大的赞赏。我还想问，如果您对我需要实现的代码有任何指示，以便执行我试图通过该程序实现的操作，请继续友善地指出这些。多谢你们。我的代码是:

import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

public class Record {

// Create an array to hold the Student's info & List to hold those student's
static Object[] student = new Object[10];
static List<Object> database = new ArrayList<Object>();

// Create Student's info variables
private int studentID;
private String lastName;
private String firstName;
private long phoneNumber;
private String major;
private double gpa;
private int birthYear;
private String birthMonth;
private int birthDay;
private String homeAddress;

/* For FUTURE tasks */
public void setStudentID( int idGiven ) {

    studentID = idGiven;
}

public void setLastName( String lastNameGiven ) {

    lastName = lastNameGiven;
}

public void setFirstName( String firstNameGiven ) {

    firstName = firstNameGiven;
}

public void setPhoneNumber( long numGiven ) {

    phoneNumber = numGiven;
}

public void setMajor( String majorGiven ) {

    major = majorGiven;
}

public void setGPA( double gpaGiven ) {

    gpa = gpaGiven;
}

public void setBirthYear( int birthYearGiven ) {

    birthYear = birthYearGiven;
}

public void setBirthMonth( String birthMonthGiven ) {

    birthMonth = birthMonthGiven;
}

public void setBirthDay( int birthDayGiven ) {

    birthDay = birthDayGiven;
}

public void setHomeAddress( String homeAddressGiven ) {

    homeAddress = homeAddressGiven;
}

// Function to create new student when one is entered
static public Object[] newStudent( int newStudentID, String newLastName, String newFirstName, long newPhoneNumber, String newMajor, double newGPA, int newBirthYear, String newBirthMonth, int newBirthDay, String newHomeAddress )
{

    student[0] = newStudentID;
    student[1] = newLastName;
    student[2] = newFirstName;
    student[3] = newPhoneNumber;
    student[4] = newMajor;
    student[5] = newGPA;
    student[6] = newBirthYear;
    student[7] = newBirthMonth;
    student[8] = newBirthDay;
    student[9] = newHomeAddress;

    database.addAll(Arrays.asList(student));



    return student;
}

// Create Function to add the student array to the database list
static public List<Object> addStudent ( Object[] s ) {

    student = s;
    database.add(student);

    return database;
}

// Test Program
public static void main( String [] args ) 
{
    Object[] student1 = Record.newStudent(00000000, "Thomas", "Luke", 9038189888L, "Computer Science", 4.00, 1997, "February", 28, "169 Karen Dr.");
    Object[] student2 = Record.newStudent(00000001, "Doe", "Jane", 5802679999L, "Mathematics", 3.62, 1990, "March", 1, "100 Circle Dr.");
    Object[] student3 = Record.newStudent(00000002, "Baker", "Joe", 9805776452L, "Safety", 2.75, 1998, "December", 7, "200 Circle Dr.");
    //Object[] student4 = Record.newStudent(00000003, "Williams", "Doug", 9407778888L, "Business", 1.95, 2000, "May", 7, "501 West Maple St.");

    Record.addStudent(student1);
    Record.addStudent(student2);
    Record.addStudent(student3);
    //Record.addStudent(student4);

    //Print out Student1's Info from the created student & from its index in the List containing all students
    System.out.println(Arrays.toString(student1));
    System.out.println(database.get(0));

    /* PERFORM TASKS: 
     * 1. delete record(s) from student id 
     * 2. list all student info in the order they were saved
     * 3. Reorder/organize student info ascending & descending by id, gpa, or birthday
     * 4. list students in a given major or given id
     */
}


}

Answer 1

“如果”你绝对只能使用数组来存储学生信息，这对我来说似乎是错误的，那么在newStudent中，你必须每次创建一个新数组时间

static public Object[] newStudent( int newStudentID, String newLastName, String newFirstName, long newPhoneNumber, String newMajor, double newGPA, int newBirthYear, String newBirthMonth, int newBirthDay, String newHomeAddress )
{

    Object[] student = new Object[10];
    student[0] = newStudentID;
    student[1] = newLastName;
    student[2] = newFirstName;
    student[3] = newPhoneNumber;
    student[4] = newMajor;
    student[5] = newGPA;
    student[6] = newBirthYear;
    student[7] = newBirthMonth;
    student[8] = newBirthDay;
    student[9] = newHomeAddress;

    database.add(student);

    return student;
}

然后您应该将整个数组(按原样)添加到 ArrayList

然而，这对我来说似乎违反直觉。相反，您应该从“学生”的概念开始，例如......

public class Student {

    private int studentID;
    private String lastName;
    private String firstName;
    private long phoneNumber;
    private String major;
    private double gpa;
    private int birthYear;
    private String birthMonth;
    private int birthDay;
    private String homeAddress;

    public Student(int studentID, String lastName, String firstName, long phoneNumber, String major, double gpa, int birthYear, String birthMonth, int birthDay, String homeAddress) {
        this.studentID = studentID;
        this.lastName = lastName;
        this.firstName = firstName;
        this.phoneNumber = phoneNumber;
        this.major = major;
        this.gpa = gpa;
        this.birthYear = birthYear;
        this.birthMonth = birthMonth;
        this.birthDay = birthDay;
        this.homeAddress = homeAddress;
    }

    public int getStudentID() {
        return studentID;
    }

    public String getLastName() {
        return lastName;
    }

    public String getFirstName() {
        return firstName;
    }

    public long getPhoneNumber() {
        return phoneNumber;
    }

    public String getMajor() {
        return major;
    }

    public double getGpa() {
        return gpa;
    }

    public int getBirthYear() {
        return birthYear;
    }

    public String getBirthMonth() {
        return birthMonth;
    }

    public int getBirthDay() {
        return birthDay;
    }

    public String getHomeAddress() {
        return homeAddress;
    }

    @Override
    public String toString() {
        return "Student{" + "studentID=" + studentID + ", lastName=" + lastName + ", firstName=" + firstName + ", phoneNumber=" + phoneNumber + ", major=" + major + ", gpa=" + gpa + ", birthYear=" + birthYear + ", birthMonth=" + birthMonth + ", birthDay=" + birthDay + ", homeAddress=" + homeAddress + '}';
    }

}

然后可以通过某种“数据库”进行管理......

public class Database {
    private List<Student> records;

    public Database() {
        records = new ArrayList<>(25);
    }

    public void add(Student student) {
        // First make sure there are a no duplictes
        records.add(student);
    }

    public Student get(int at) {
        return records.get(at);
    }

    public Student remove(int at) {
        return records.remove(at);
    }

    public int size() {
        return records.size();
    }
}

就我个人而言，我会使用Database来创建Student的新实例，但我可能已经偏离主题了

然后你可以使用它，比如......

Database database = new Database();

database.add(new Student(00000000, "Thomas", "Luke", 9038189888L, "Computer Science", 4.00, 1997, "February", 28, "169 Karen Dr."));
database.add(new Student(00000001, "Doe", "Jane", 5802679999L, "Mathematics", 3.62, 1990, "March", 1, "100 Circle Dr."));
database.add(new Student(00000002, "Baker", "Joe", 9805776452L, "Safety", 2.75, 1998, "December", 7, "200 Circle Dr."));

//Print out Student1's Info from the created student & from its index in the List containing all students
for (int index = 0; index < database.size(); index++) {
    System.out.println(database.get(index));
}

这会打印出类似...的内容

Student{studentID=0, lastName=Thomas, firstName=Luke, phoneNumber=9038189888, major=Computer Science, gpa=4.0, birthYear=1997, birthMonth=February, birthDay=28, homeAddress=169 Karen Dr.}
Student{studentID=1, lastName=Doe, firstName=Jane, phoneNumber=5802679999, major=Mathematics, gpa=3.62, birthYear=1990, birthMonth=March, birthDay=1, homeAddress=100 Circle Dr.}
Student{studentID=2, lastName=Baker, firstName=Joe, phoneNumber=9805776452, major=Safety, gpa=2.75, birthYear=1998, birthMonth=December, birthDay=7, homeAddress=200 Circle Dr.}