用双向链表作数据结构，用java语言编写一个通讯录管理系统，本系统应完成一下几方面的功能： 1)输入信息——enter(); 2)显示信息———display( ); 3)查找以姓名作为关键字 ———search( ); 4)删除信息———delete( ); 5)存盘———save ( ); 6)装入———load( ) ; 设计要求： 1)每条信息至包含 ：姓名（NAME ）街道（STREET）城市（CITY）邮编（EIP）国家（STATE）几项 2)作为一个完整的系统，应具有友好的界面和较强的容错能力，上机能正常运行 3）具有可视化界面

好的，我已经记录下来了你的问题。对于你的问题，我可以给出以下回答：

实现双向链表可以使用Java的LinkedList类，该类实现了List接口，同时也是一个双向链表。通讯录管理系统的实现可以借助该类来完成。

下面是一个简单的通讯录管理系统的代码示例：

import java.io.*;
import java.util.*;

class Contact {
    String name;
    String street;
    String city;
    int zip;
    String state;
}

class ContactList {
    LinkedList<Contact> contacts = new LinkedList<Contact>();

    public void enter() {
        Contact contact = new Contact();
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter name: ");
        contact.name = scanner.nextLine();
        System.out.print("Enter street: ");
        contact.street = scanner.nextLine();
        System.out.print("Enter city: ");
        contact.city = scanner.nextLine();
        System.out.print("Enter zip: ");
        contact.zip = scanner.nextInt();
        scanner.nextLine();
        System.out.print("Enter state: ");
        contact.state = scanner.nextLine();
        contacts.add(contact);
    }

    public void display() {
        for (Contact contact : contacts) {
            System.out.println("Name: " + contact.name);
            System.out.println("Street: " + contact.street);
            System.out.println("City: " + contact.city);
            System.out.println("Zip: " + contact.zip);
            System.out.println("State: " + contact.state);
        }
    }

    public void search(String name) {
        boolean found = false;
        for (Contact contact : contacts) {
            if (contact.name.equals(name)) {
                System.out.println("Name: " + contact.name);
                System.out.println("Street: " + contact.street);
                System.out.println("City: " + contact.city);
                System.out.println("Zip: " + contact.zip);
                System.out.println("State: " + contact.state);
                found = true;
                break;
            }
        }
        if (!found) {
            System.out.println("Contact not found.");
        }
    }

    public void delete(String name) {
        Iterator<Contact> iterator = contacts.iterator();
        while (iterator.hasNext()) {
            Contact contact = iterator.next();
            if (contact.name.equals(name)) {
                iterator.remove();
                System.out.println("Contact deleted.");
                return;
            }
        }
        System.out.println("Contact not found.");
    }

    public void save() {
        try {
            ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream("contacts.dat"));
            outputStream.writeObject(contacts);
            outputStream.close();
            System.out.println("Contacts saved.");
        } catch (IOException e) {
            System.out.println("Error saving contacts.");
        }
    }

    public void load() {
        try {
            ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream("contacts.dat"));
            contacts = (LinkedList<Contact>)inputStream.readObject();
            inputStream.close();
            System.out.println("Contacts loaded.");
        } catch (IOException e) {
            System.out.println("Error loading contacts.");
        } catch (ClassNotFoundException e) {
            System.out.println("Error loading contacts.");
        }
    }
}

public class ContactManager {
    public static void main(String[] args) {
        ContactList contactList = new ContactList();
        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.println("1. Enter contact");
            System.out.println("2. Display contacts");
            System.out.println("3. Search contacts");
            System.out.println("4. Delete contact");
            System.out.println("5. Save contacts");
            System.out.println("6. Load contacts");
            System.out.println("7. Exit");
            System.out.print("Enter choice: ");
            int choice = scanner.nextInt();
            scanner.nextLine();
            switch (choice) {
                case 1:
                    contactList.enter();
                    break;
                case 2:
                    contactList.display();
                    break;
                case 3:
                    System.out.print("Enter name to search: ");
                    String name = scanner.nextLine();
                    contactList.search(name);
                    break;
                case 4:
                    System.out.print("Enter name to delete: ");
                    name = scanner.nextLine();
                    contactList.delete(name);
                    break;
                case 5:
                    contactList.save();
                    break;
                case 6:
                    contactList.load();
                    break;
                case 7:
                    System.exit(0);
                    break;
                default:
                    System.out.println("Invalid choice.");
                    break;
            }
        }
    }
}

该代码示例使用了一个Contact类来表示每个联系人，该类中包含了姓名、街道、城市、邮编和国家等信息。ContactList类则是一个管理联系人的类，它使用LinkedList来存储联系人列表，并提供了enter()、display()、search()、delete()、save()和load()等方法来进行联系人的添加、显示、查找、删除、存储和加载等操作。最后，ContactManager类是一个简单的控制台程序，它通过一个循环来接受用户的输入，并调用ContactList类的相应方法来完成操作。