Java继承，在构造函数内对父类初始化的问题

最新推荐文章于 2024-08-27 21:54:03 发布

BalterNotz

最新推荐文章于 2024-08-27 21:54:03 发布

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分类专栏：原创-Java 文章标签： Java 构造函数

本文链接：https://blog.youkuaiyun.com/BalterNotz/article/details/52558842

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本文通过一个具体的Java程序示例，展示了如何正确实现类的继承，并详细解释了构造函数调用的过程。对比了两种创建子类对象的方法，一种是通过super关键字调用父类构造函数，另一种则是直接在子类构造函数中赋值，后者会导致编译错误。

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source: https://www.hackerrank.com/challenges/30-inheritance?h_r=next-challenge&h_v=zen

Student的创造方法，这样子写：

    Student(String firstName, String lastName, int id, int[] testScores) {
        super(firstName, lastName, id);
        this.testScores = testScores;
    }

是可以的，

但，若这样子写：

    Student(String firstName, String lastName, int id, int[] testScores) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.idNumber = id;
        this.testScores = testScores;
    }

就会报错：如下：

Solution.java:26: error: constructor Person in class Person cannot be applied to given types;
    Student(String firstName, String lastName, int id, int[] testScores) {
                                                                         ^
  required: String,String,int
  found: no arguments
  reason: actual and formal argument lists differ in length
1 error

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;

    Student(String firstName, String lastName, int id, int[] testScores) {
        super(firstName, lastName, id);
        this.testScores = testScores;
    }

    public char calculate(){
        int avg = Arrays.stream(testScores).sum()/testScores.length;
        if (avg >= 90) return 'O';
        if (avg >= 80) return 'E';
        if (avg >= 70) return 'A';
        if (avg >= 55) return 'P';
        if (avg >= 40) return 'D';
        return 'T';
    }
}

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() );
   }
}