对象引用如何在包装类、对象和自定义对象中工作？

Question

考虑下面的代码：

class Student{
    int id;
    String name;
}

public class Main
{
    public static void main(String[] args) {
        
        Student s1 = new Student();
        s1.id = 10;
        s1.name = "student 1";
        
        Student s2 = new Student();
        s2.id = 20;
        s2.name = "student 2";
        
        Student s3 = s1;
        s3.name = "student 3";
        
        System.out.println(s1.id +" "+s1.name);
        System.out.println(s3.id +" "+s3.name);
    }
}

对于上面的代码，输出是：

10 student 3
10 student 3

public class Main
{
    public static void main(String[] args) {
        
        Integer a = 10;
        Integer b = 20;
        Integer c = a;
        
        c = 30;
        
        System.out.println(a);
        System.out.println(c);
    }
}

10
30

Answer 1

s1指内存的一部分，让我们调用该部分a。将s1分配给s3后，s3也将指a；这意味着s1和s3都有指向同一个内存块的指针。改变s1或s3实际上是改变该存储块中的数据；并且会影响到两者。