Directly output the object name

package basic.java;

public class Case {
    public static void main(String[] args) {
        Student s = new Student();
        System.out.println(s);
    }
}

basic.java.Student@19bb25a

输出的结果是包名.

package basic.java;

public class Case {
    public static void main(String[] args) {
        Student s = new Student();
        System.out.println(s);
        System.out.println(s.name);
        System.out.println(s.age);
    }
}

basic.java.Student@1e58cb8
null
0

String是一个引用类型的类，所以默认输出的是null。