java 内部类 用法

package com.jingshan;import com.jingshan.Person.Student1;import com.jingshan.Person.Student2;import com.jingshan.Person.Student3;public class Person {    public static void main(String[] args) {        Person p = new Person();        Student1 s1 = p.new Student1();        Student2 s2 = p.new Student2();        Student3 s3 = p.new Student3();        Student4 s4 = p.new Student4();        Student5 s5 = new Student5();    }    public class Student1{        public Student1() {            System.out.print("s1");        }    }    class Student2{        public Student2() {            System.out.print("s2");        }    }    protected class Student3{        public Student3() {            System.out.print("s3");        }    }    private class Student4{        public Student4() {            System.out.print("s4");        }    }    static class Student5{        public Student5() {            System.out.print("s5");        }    }}