Question

尝试解决psvm中的错误，老实说，我不知道什么是错的或google与此有关。它不会让我发布这个没有更多的话，但我没有知道什么是错误的程序，以提供更多的细节。

public class backToSchoolDalton{
        public class Person{
            //Person Code
        public class Teacher extends Person{
            //TeacherCode
        public class Student extends Person{
            //StudentCode
        public class CollegeStudent extends Student {
            //CollegeStudentCode
        public static void main(String[] args) {

        ERROR HEAVEN RIGHT HERE

        backToSchoolDalton a = new backToSchoolDalton();
        backToSchoolDalton b = new backToSchoolDalton();
        backToSchoolDalton c = new backToSchoolDalton();
        backToSchoolDalton d = new backToSchoolDalton();
        a.Person("Coach Bob", 27, "M");
        b.Student("Lynne Brooke", 16, "F", "HS95129", 3.5);
        c.Teacher("Duke Java", 34, "M", "Computer Science", 50000);
        d.CollegeStudent("Ima Frosh", 18, "F", "UCB123",
                4.0, 1, "English");

        Person bob = new Person("Coach Bob", 27, "M");
        System.out.println(bob);

        Student lynne = new Student("Lynne Brooke", 16, "F", "HS95129", 3.5);
        System.out.println(lynne);

        Teacher mrJava = new Teacher("Duke Java", 34, "M", "Computer Science", 50000);
        System.out.println(mrJava);

        CollegeStudent ima = new CollegeStudent("Ima Frosh", 18, "F", "UCB123",
                4.0, 1, "English");
        System.out.println(ima);
    }
}

请帮忙！

Answer 1

public static void main(String[] args) {
    backToSchoolDalton s = new backToSchoolDalton();

    Person bob = s.new Person("Coach Bob", 27, "M");
    System.out.println(bob);

    Student lynne = s.new Student("Lynne Brooke", 16, "F", "HS95129", 3.5);
    System.out.println(lynne);

    Teacher mrJava = s.new Teacher("Duke Java", 34, "M", "Computer Science", 50000);
    System.out.println(mrJava);

    CollegeStudent ima = s.new CollegeStudent("Ima Frosh", 18, "F", "UCB123",
            4.0, 1, "English");
    System.out.println(ima);
}

Answer 2

有两种（常见）类型的嵌套类。 Inner classes and static nested classes.内部类与其周围类的实例耦合，这意味着您需要在使用它之前构造周围类的实例。另一方面，静态嵌套类不是。它就像任何其他类一样，除非出于组织原因在另一个类中定义。

您发布的用于构建backToSchoolDalton实例的解决方案之所以有效，是因为您现在拥有了周围类的实例。但这实际上并不是你想要的。相反，只需将内部类设置为静态嵌套类，就可以直接构造这些类。

public static class Person {
  //Person Code
}

public static class Teacher extends Person {
  //TeacherCode
}

...

Teacher c = new Teacher("Duke Java", 34, "M", "Computer Science", 50000);

Answer 3

编辑：我的下面的回答是错误的。只要该类在构造函数中没有这样做，就可以在同一个类中创建一个类的实例。不删除我的答案，以便其他人可以从我的错误中吸取教训

据我所知，你不能在同一个类中声明一个类的实例。你需要将main（）移到backtoSchoolDalton（）之外：

backToSchoolDalton() {
    //dalton code
}

public static void main(String[] args) {

    backToSchoolDalton a = new backToSchoolDalton();
    backToSchoolDalton b = new backToSchoolDalton();
    backToSchoolDalton c = new backToSchoolDalton();
    backToSchoolDalton d = new backToSchoolDalton();
    a.Person("Coach Bob", 27, "M");
    b.Student("Lynne Brooke", 16, "F", "HS95129", 3.5);
    c.Teacher("Duke Java", 34, "M", "Computer Science", 50000);
    d.CollegeStudent("Ima Frosh", 18, "F", "UCB123",
        4.0, 1, "English");

    Person bob = new Person("Coach Bob", 27, "M");
    System.out.println(bob);

    Student lynne = new Student("Lynne Brooke", 16, "F", "HS95129", 3.5);
    System.out.println(lynne);

    Teacher mrJava = new Teacher("Duke Java", 34, "M", "Computer Science",
    50000);
    System.out.println(mrJava);

    CollegeStudent ima = new CollegeStudent("Ima Frosh", 18, "F", "UCB123",
        4.0, 1, "English");
    System.out.println(ima);

}

main不会运行类中包含的类

3 个答案: