java1、用单链表表方式实现在线通讯录的设计，可以对通讯录作插入、删除、显示、查找、修改等操作

以下是Java单链表实现在线通讯录的代码：

import java.util.Scanner;

class Contact {
    String name;
    String phone;
    Contact next;
    
    public Contact(String name, String phone) {
        this.name = name;
        this.phone = phone;
        this.next = null;
    }
}

class ContactList {
    Contact head;
    
    public ContactList() {
        this.head = null;
    }
    
    public void insert(Contact contact) {
        if (head == null) {
            head = contact;
        } else {
            Contact curr = head;
            while (curr.next != null) {
                curr = curr.next;
            }
            curr.next = contact;
        }
        System.out.println("Successfully added " + contact.name + " to the contact list.");
    }
    
    public void display() {
        if (head == null) {
            System.out.println("No contacts found.");
        } else {
            Contact curr = head;
            System.out.println("Contact List:");
            while (curr != null) {
                System.out.println("Name: " + curr.name + ", Phone: " + curr.phone);
                curr = curr.next;
            }
        }
    }
    
    public void search(String name) {
        if (head == null) {
            System.out.println("No contacts found.");
        } else {
            Contact curr = head;
            while (curr != null) {
                if (curr.name.equals(name)) {
                    System.out.println("Name: " + curr.name + ", Phone: " + curr.phone);
                    return;
                }
                curr = curr.next;
            }
            System.out.println("Contact not found.");
        }
    }
    
    public void delete(String name) {
        if (head == null) {
            System.out.println("No contacts found.");
        } else if (head.name.equals(name)) {
            head = head.next;
            System.out.println("Contact " + name + " has been deleted.");
        } else {
            Contact prev = head;
            Contact curr = head.next;
            while (curr != null) {
                if (curr.name.equals(name)) {
                    prev.next = curr.next;
                    System.out.println("Contact " + name + " has been deleted.");
                    return;
                }
                prev = curr;
                curr = curr.next;
            }
            System.out.println("Contact not found.");
        }
    }
    
    public void modify(String name, String phone) {
        if (head == null) {
            System.out.println("No contacts found.");
        } else {
            Contact curr = head;
            while (curr != null) {
                if (curr.name.equals(name)) {
                    curr.phone = phone;
                    System.out.println("Contact " + name + " has been modified.");
                    return;
                }
                curr = curr.next;
            }
            System.out.println("Contact not found.");
        }
    }
}

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        ContactList contactList = new ContactList();
        while (true) {
            System.out.println("Please select an operation:");
            System.out.println("1. Add a contact");
            System.out.println("2. Display contacts");
            System.out.println("3. Search for a contact");
            System.out.println("4. Delete a contact");
            System.out.println("5. Modify a contact");
            System.out.println("6. Exit");
            int choice = sc.nextInt();
            sc.nextLine();
            switch (choice) {
                case 1:
                    System.out.println("Please enter the name:");
                    String name = sc.nextLine();
                    System.out.println("Please enter the phone number:");
                    String phone = sc.nextLine();
                    Contact contact = new Contact(name, phone);
                    contactList.insert(contact);
                    break;
                case 2:
                    contactList.display();
                    break;
                case 3:
                    System.out.println("Please enter the name:");
                    name = sc.nextLine();
                    contactList.search(name);
                    break;
                case 4:
                    System.out.println("Please enter the name:");
                    name = sc.nextLine();
                    contactList.delete(name);
                    break;
                case 5:
                    System.out.println("Please enter the name:");
                    name = sc.nextLine();
                    System.out.println("Please enter the new phone number:");
                    phone = sc.nextLine();
                    contactList.modify(name, phone);
                    break;
                case 6:
                    System.exit(0);
                default:
                    System.out.println("Invalid choice.");
                    break;
            }
        }
    }
}

使用单链表方式实现在线通讯录的设计，可以对通讯录作插入、删除、显示、查找、修改等操作。通过控制台输入，用户可以选择相应的操作。如果用户选择添加联系人，则需要输入姓名和电话号码，程序将自动将联系人添加到通讯录中。如果用户选择查看联系人，则程序将显示所有联系人的姓名和电话号码。如果用户选择查找联系人，则需要输入联系人姓名，程序将在通讯录中查找该联系人并显示其姓名和电话号码。如果用户选择删除联系人，则需要输入联系人姓名，程序将从通讯录中删除该联系人。如果用户选择修改联系人，则需要输入联系人姓名和新的电话号码，程序将修改联系人的电话号码。如果用户选择退出，则程序将退出。