这些类的继承关系有些类似，弄一个作为样例，理解一下其中的机制。

package cc.openhome;import java.io.*;public class Member {    private String number;    private String name;    private int age;        public Member(String number, String name, int age) {        this.number = number;        this.name = name;        this.age = age;    }        @Override    public String toString() {        return String.format("(%s, %s, %d)", number, name, age);    }        public void save() {        try{            DataOutputStream output = new DataOutputStream(new FileOutputStream(number));            output.writeUTF(number);            output.writeUTF(name);            output.writeInt(age);        } catch(IOException ex) {            throw new RuntimeException(ex);        }    }        public static Member load(String number) {        Member member = null;        try {                        DataInputStream input = new DataInputStream(new FileInputStream(number));            member = new Member(input.readUTF(), input.readUTF(), input.readInt());        } catch(IOException ex) {            throw new RuntimeException(ex);        }        return member;    }}

package cc.openhome;import java.io.*;public class MemberDemo {    public static void main(String[] args) {        Member[] members = { new Member("B1234", "Justing", 90),new Member("B4532", "Monica", 87)};        for(Member member : members) {            member.save();        }        System.out.println(Member.load("B1234"));    }}