Question

我正在上Java课，这个问题与我要完成的一个练习有关。我试图打印出从抽象超类的2个子类创建的对象数组的内容。我能够创建对象并将它们存储在一个数组中，但是当我打印出数组的内容时，我只能获得超类的“age”和“weight”属性的最后一个实例。如您所见，它们是私有属性。有没有办法在创建对象时访问这些属性的值？我做了一些阅读，我很困惑，我是否可以做到，如果可以，那怎么样？我的代码：

public abstract class Parent {
    private static int age;
    private static double weight;
    public Animal(int age, double weight) {
        this.age = age;
        this.weight = weight;
        }
    public static int getAge() {
        return age;
        }
    public static double getWeight() {
        return weight;
        }
    }

public class Child1 extends Parent {
    private String name, owner, petInfo;
    protected int age;
    protected double weight;
    public Child1(int age, double weight, String name, String owner) {
        super(age, weight);
        this.name = name;
        this.owner = owner;
        }
    public String toString() {
        petInfo = "Pet's name: " + this.getName() + "\nPet's age: " + getAge() + " years\nPet's weight: " + getWeight() + " kilos\nOwner's name: " + this.getOwner();
        return petInfo;
        }
    }

public class Child2 extends Parent {
    public String wildInfo;
    public Child2(int age, double weight) {
        super(age, weight);
        }
    public String toString() {
        wildInfo = "The wild animal's age: " + getAge() + "\nThe wild animal's weight: " + getWeight();
        return wildInfo;
        }
    }

public class Console {
    public static void main(String[] args) {
        Parent ref[] = new Parent[5];
        for(i = 0; i < 5; i++) {
        //user input here
        Child1 pet = new Child1(age, weight, name, owner);
        ref[i] = pet;
        //more user input
        Child2 wild = new Child2(age, weight);
        ref[i] = wild;
        }
        //print contents of array
        for(Parent item : ref)
            System.out.println("\n" +item.toString()+ "\n");

我的理解是我只能通过方法访问超类的属性。当我在toString（）中使用getAge（）和getWeight（）方法时，我没有得到为每个对象输入的值，只有属性的最后一个值。任何帮助将不胜感激。欢呼声。

Answer 1

不要对年龄和体重使用静态变量：

private static int age;
private static double weight;

静态变量的值对于此类型的所有对象都是相同的，因为这些变量是 class 变量，而不是实例变量。这些人应该是实例或非静态字段，这将使它们对于此类的每个实例（或子类的实例）都是唯一的。

然后在你的Child类中，去掉这些阴影变量，因为它们会遮蔽Parent类中类似命名的字段：

public class Child1 extends Parent {
    private String name, owner, petInfo;
    protected int age;            // ***** get rid of, since it shadows
    protected double weight;      // ***** get rid of, since it shadows

相反，无论你在哪里使用它们，都要使用Child类中的getter和setter。

Answer 2

上述程序中存在错误。

将父类中的静态方法更正为非静态方法。

示例代码：

import java.util.Scanner;

    abstract class Parent {
        private int age;
        private double weight;
        public Parent(int age, double weight) {
            this.age = age;
            this.weight = weight;
            }
        public int getAge() {
            return age;
            }
        public double getWeight() {
            return weight;
            }
    }

    class Child1 extends Parent {
        private String name, owner, petInfo;
        public Child1(int age, double weight, String name, String owner) {
            super(age, weight);
            this.name = name;
            this.owner = owner;
            }
        public String toString() {
            petInfo = "Pet's name: " + this.getName() + "\nPet's age: " + getAge() + " years\nPet's weight: " + getWeight() + " kilos\nOwner's name: " + this.getOwner();
            return petInfo;
            }
        public String getName() {
            return name;
        }
        public String getOwner() {
            return owner;
        }
    }

    class Child2 extends Parent {
        public String wildInfo;
        public Child2(int age, double weight) {
            super(age, weight);
            }
        public String toString() {
            wildInfo = "The wild animal's age: " + getAge() + "\nThe wild animal's weight: " + getWeight();
            return wildInfo;
            }
        }

    public class Console {
        public static void main(String[] args) {
            Scanner in = new Scanner(System.in);
            Parent ref[] = new Parent[2];
            //int weight=10;
            //int age=5;
            //String name="parrot";
            //String owner="rajesh";
            for(int i = 0; i < 2; i++) {
            System.out.println("Enter the name");
            String name=in.next();
            System.out.println("Enter the age ");
            int age=in.nextInt();
            System.out.println("Enter the weight");
            double weight=in.nextDouble();
            System.out.println("Enter the owner");
            String owner=in.next();
            //user input here
            Child1 pet = new Child1(age, weight, name, owner);
            ref[i] = pet;
            //more user input
            if (i==1)
            {
                break;
            }
            System.out.println("Enter the name");
            name=in.next();
            System.out.println("Enter the age ");
            age=in.nextInt();
            System.out.println("Enter the weight");
            weight=in.nextDouble();
            System.out.println("Enter the owener");
            owner=in.next();
            Child2 wild = new Child2(age, weight);
            ref[++i] = wild;
            }
            //print contents of array
            for(Parent item : ref)
                System.out.println("\n" +item.toString()+ "\n");
        }
    }

如何在子类对象中的抽象类中访问私有属性的值？

2 个答案: