仍在努力理解Java中的面向对象编程

Question

假设有一个名为Hello的类，我如何将名为var1和var2的变量声明为类Hello中对象的引用？ 我以为只是你好，var1，var2

另外，如果只使用默认构造函数构造类Hello的对象的实例，那么它就是Hello Hello=new Hello（）

最后，我的最后一个问题是，如果我要使用默认构造函数实例化Hello类的一个对象，并将该对象分配给名为var1的varaible，那么它就是Hello var1=new Hellow（）；。如何将对名为var1的对象的引用分配给名为var2的变量

我知道有一个术语来描述变量var1和var2的当前状态，但我想不起来

Answer 1

只是给出了一个测试例子来说明这些事情

public class Hello {
    Hello var1, var2;
    public static void main(String[] args){
        Hello h1 = new Hello();
        h1.var1 = h1;
        System.out.println("h1.var1    "+ h1.var1);

        Hello h2 = new Hello();
        h1.var2 = h2;
        System.out.println("h1.var2    "+ h1.var2);

        h1.var2 = h1.var1;

        System.out.println("h1.var1    "+ h1.var1);
        System.out.println("h1.var2    "+ h1.var2);
    }
}


    Output :- 

    h1.var1    Hello@19e0bfd
    h1.var2    Hello@139a55
    h1.var1    Hello@19e0bfd
    h1.var2    Hello@19e0bfd

Assuming there is a class named Hello, How would I declare variables named var1 and var2 to be references to objects in the class Hello? I assumed it would just be Hello var1, var2;

您可以看到，有两个声明为同一类的变量可以引用Hello类实例

Also to just construct an instance of the object of the class Hello using the default constructor would it just be Hello hello = new Hello();

是的，每个类都有默认的构造函数，所以你可以像这样初始化类

Finally my last question is if I were to instantiate an object of the class Hello using the default constructor and assign that object to the varaible named var1 it would just be Hello var1 = new Hellow();. How would I assign the reference to the object named var1 to the variable named var2

正如您看到的输出，var2的哈希代码与h1.var2 = h1.var1语句之后的var1相同。这表明var2之前的引用被var1引用替换。所以这里不复制对象，而是复制对对象的引用。检查{}和{}的相同{}

就这样