java - 错误 "No Closing Instance..."

Question

我是 Java 新手，最近我研究了类和对象主题。但是，我无法继续执行此代码:

public class ClassStudy {

// Student Group
class Student {

    public String name = null;
    public String surname = null;

    boolean study(boolean does) {
        // He studies.
        boolean d = does;
        return d;
    }
    boolean slackOff(boolean does) {
        // He slacks off.
        boolean d = does;
        return d;
    }
}

// Teacher Group
class Teacher {

    public String name = null;
    public String surname = null;

    boolean teach(boolean does) {
        // He teaches.
        boolean d = does;
        return d;
    }
    boolean learn(boolean does) {
        // He learns.
        boolean d = does;
        return d;
    }
}

// Main Method
public static void main(String[] args) {
    Student student = new Student();
    Teacher teacher = new Teacher();
}

}

在main方法中，我得到了学生的错误，但没有得到老师的错误。我不知道我是否做错了或者我看不到它。必须做什么？

我得到的错误:

• The value of the local variable student is not used
  • No enclosing instance of type ClassStudy is accessible. Must qualify the allocation with an enclosing instance of type ClassStudy (e.g. x.new A() where x is an instance of ClassStudy).
  • Line breakpoint:ClassStudy [line: 44] - main(String[])

Answer 1

要么将Student(和Teacher)类设为静态，要么将其设为顶级类

static class Student {
   ...
}