Java 子類有參構造器報錯

Java 子類的有參構造器報錯：Implicit super constructor Person() is undefined. Must explicitly invoke another constructor

 

 

 

 

import java.util.*;

class Person {
    protected String firstName;
    protected String lastName;
    protected int idNumber;
    
    // Constructor
    Person(String firstName, String lastName, int identification){
        this.firstName = firstName;
        this.lastName = lastName;
        this.idNumber = identification;
    }
    
    // Print person data
    public void printPerson(){
         System.out.println(
                "Name: " + lastName + ", " + firstName 
            +     "\nID: " + idNumber); 
    }
     
}

class Student extends Person{
    private int[] testScores;

    /*    
    *   Class Constructor
    *   
    *   @param firstName - A string denoting the Person's first name.
    *   @param lastName - A string denoting the Person's last name.
    *   @param id - An integer denoting the Person's ID number.
    *   @param scores - An array of integers denoting the Person's test scores.
    */
    // Write your constructor here
    Student(String firstName, String lastName, int id,  int[] scores){

　　　　　super()； //隱藏會執行的默認構造器 super(firstName, lastName, id); //因為少了父類自定義構造器初始化，所以會報錯 this.firstName = firstName;
        this.lastName = lastName;
        this.idNumber = id;
        this.testScores = scores;
    }

    /*    
    *   Method Name: calculate
    *   @return A character denoting the grade.
    */
    // Write your method here
    public char calculate(){
        int num = testScores.length;
        int s = 0;
        for(int score : testScores) {
            s = s + score;
        }
        s = s/num;

        char grade = '-';
        if(s>=90&&s<=100){
            grade = 'O';
        }else if(s>=80&&s<90){
            grade = 'E';
        }else if(s>=70&&s<80){
            grade = 'A';
        }else if(s>=55&&s<70){
            grade = 'P';
        }else if(s>=40&&s<55){
            grade = 'D';
        }else if(s<40){
            grade = 'T';
        }
        return grade;
    }
}

class Solution {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String firstName = scan.next();
        String lastName = scan.next();
        int id = scan.nextInt();
        int numScores = scan.nextInt();
        int[] testScores = new int[numScores];
        for(int i = 0; i < numScores; i++){
            testScores[i] = scan.nextInt();
        }
        scan.close();
        
        Student s = new Student(firstName, lastName, id, testScores);
        s.printPerson();
        System.out.println("Grade: " + s.calculate());
    }
}

原因：父類的構造方法Person()只有有參數的構造方法，也可以說   父類沒有無參的構造方法(即默認的super()初始化會報錯) ，這樣的話，子類繼承該類，就必須要顯示的調用父類的構造函數，這樣才能保證，編譯器在將子類初始化前，父類先被初始化。