如何使用Java中的另一个对象制作一个对象？

如何解决如何使用Java中的另一个对象制作一个对象？

我正在定义Dog类的特征，其中包含定义其名称和年龄的实例数据，为该数据创建构造函数，setter-getter方法等。我也有一种返回“ dog years”值的方法（也就是人类同等年龄的7倍。我有一个驱动程序类Kennel，该类的主要方法将实例化并更新这些Dog对象，并将其打印出来。

在Kennel类中，我的最后一条语句中可以看到一条注释，内容为““在某点上询问”。 即：//Dog dog3 = dog2.setName("Krypto"); 在评论中，我尝试通过setName方法向它分配其余dog2对象数据的同时创建一个名为“ Kryto”的新Dog对象。换句话说，我希望我的dog3对象具有dog2的所有特征，但名称除外。

实现此目标的方式是什么？我知道我不能使用对象作为参数，对吧？

这是下面两个类的代码：

Kennel (Driver):

    public class Kennel {
    //instance data
    int age;
    public static void main(String[] args) {
        //dog objects
        Dog dog1 = new Dog("Bear",3);
        Dog dog2 = new Dog("Bella",7);
        
        //calling the method required to calculate the dog's human years,so that when I print these objects out,they actually have their traits
        //(that being,their "dogman" age.
        dog1.calcDogmanYears();
        dog2.calcDogmanYears();
        
        //output
        System.out.println(dog1);
        System.out.println(dog2);
        dog2.setName("Krypto");
        //Dog dog3 = dog2.setName("Krypto"); //INQUIRE AT SOME POINT
        System.out.println(dog2);

    }

}

狗：

public class Dog {
    //instance data
    String name;
    int age;
    
    //constructor (normal) to allow objects to have values by default (i.e. no requirement of forcing parameters down the methods from the driver class)
    public Dog()    {
        name = "";
        age = 0;
        return;
    }
    
    //constructor,keep in mind for future reference,that I used different variables to allow the constructor to be overloaded in a driver class to
    //follow Chapter 4's constructor Java Syntax. We Could've overloaded the constructor with formal parameters of the same name as the instance data
    //with the "this.(insert variable here)" modifier. I did this for shits and giggles.
    public Dog(String name,int age){
        this.name = name;
        this.age = age;
        return;
    }
    
    //method to convert dog to human years
    public int calcDogmanYears() {
        age = age * 7;
        return age;
    }
        
    //setters and getters for name
    public void setName(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
    
    //mutators and accessors for age}
    public void setAge(int age) {
        this.age = age;
    }
    public int getAge() {
        return age;
    }
    
    public String toString() {
        String result = "The name of the dog is " + name + ",and their age is " + age + " years old.";
        return result;
    }
}

解决方法

一种选择是使Dog类可克隆。克隆原稿，然后适当设置name。

Dog dog3 = dog2.clone();
dog3.setName("Krypto");

内核（驱动程序）类：

public class Kennel {
    //instance data
    int age;
    public static void main(String[] args) throws CloneNotSupportedException {
        //dog objects
        Dog dog1 = new Dog("Bear",3);
        Dog dog2 = new Dog("Bella",7);
        
        //calling the method required to calculate the dog's human years,so that when I print these objects out,they actually have their traits
        //(that being,their "dogman" age.
        dog1.calcDogmanYears();
        dog2.calcDogmanYears();
        
        //output
        System.out.println(dog1);
        System.out.println(dog2);
        dog2.setName("Krypto");
        Dog dog3 = dog2.clone();
        dog3.setName("Krypto"); //INQUIRE AT SOME POINT
        System.out.println(dog2);

    }

}

更新的狗类：

public class Dog implements Cloneable {
    //instance data
    String name;
    int age;
    
    //constructor (normal) to allow objects to have values by default (i.e. no requirement of forcing parameters down the methods from the driver class)
    public Dog()    {
        name = "";
        age = 0;
    }
    // Overriding clone() method of Object class
    public Dog clone() throws CloneNotSupportedException{  
    return (Dog) super.clone();  
    }
    
    public Dog(String name,int age){
        this.name = name;
        this.age = age;
    }
    
    //method to convert dog to human years
    public int calcDogmanYears() {
        age = age * 7;
        return age;
    }
        
    //setters and getters for name
    public void setName(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
    
    //mutators and accessors for age}
    public void setAge(int age) {
        this.age = age;
    }
    public int getAge() {
        return age;
    }
    
    public String toString() {
        String result = "The name of the dog is " + name + ",and their age is " + age + " years old.";
        return result;
    }
}

输出：

狗的名字叫熊，年龄21岁。
这只狗叫贝拉（Bella），年龄49岁。
这只狗叫Krypto，年龄49岁。

,

您可以在Dog类中定义一个新方法：

public Dog createTheSameAgeDog(String name) {
    return new Dog(name,this.age);
}

然后称呼它：

Dog dog3 = dog2.createTheSameAgeDog("Krypto"); // creates the Dog (age 7,name "Krypto")