Java对象垃圾收集

Question

public class Test {

public static void main(String[] args){
    Student s1 = new Student("o1"); 
    Student s2 = new Student("o2");
    Student s3 = new Student("o3");
    s1=s3; 
    s3=s2;
    s2=null;
    //HERE
    }
}

有人能给我解释一下原因吗？

Answer 1

考虑一个简单的班级学生。

第1步：

Student s1 = new Student("s1"); 
Student s2 = new Student("s2");
Student s3 = new Student("s3");

s1、s2、s3引用堆空间中的3个对象

Student s1 = s3; 

Student s1 = s3;
Student s3 = s2;

第4步：

Student s1 = s3;
Student s3 = s2;
Student s2 = null;

变量s1引用s3堆空间

变量s3引用s2堆空间