用java写图书管理系统

好的，下面是一个简单的图书管理系统的 Java 代码示例：

import java.util.ArrayList;
import java.util.Scanner;

public class LibrarySystem {
    // 图书类
    public static class Book {
        private String title;
        private String author;
        private int numCopies;

        public Book(String title, String author, int numCopies) {
            this.title = title;
            this.author = author;
            this.numCopies = numCopies;
        }

        public String getTitle() {
            return title;
        }

        public String getAuthor() {
            return author;
        }

        public int getNumCopies() {
            return numCopies;
        }

        public void setNumCopies(int numCopies) {
            this.numCopies = numCopies;
        }
    }

    // 图书馆类
    public static class Library {
        private ArrayList<Book> books;

        public Library(ArrayList<Book> books) {
            this.books = books;
        }

        public ArrayList<Book> getBooks() {
            return books;
        }

        // 添加图书
        public void addBook(Book book) {
            books.add(book);
        }

        // 删除图书
        public void removeBook(Book book) {
            books.remove(book);
        }

        // 显示所有图书
        public void displayBooks() {
            System.out.println("图书列表：");
            for (Book book : books) {
                System.out.println(book.getTitle() + " - " + book.getAuthor() + " - " + book.getNumCopies() + "本");
            }
        }

        // 借出图书
        public void borrowBook(String title) {
            for (Book book : books) {
                if (book.getTitle().equals(title)) {
                    if (book.getNumCopies() > 0) {
                        book.setNumCopies(book.getNumCopies() - 1);
                        System.out.println("借书成功！");
                        return;
                    } else {
                        System.out.println("该书已全部借出！");
                        return;
                    }
                }
            }
            System.out.println("未找到该书！");
        }

        // 归还图书
        public void returnBook(String title) {
            for (Book book : books) {
                if (book.getTitle().equals(title)) {
                    book.setNumCopies(book.getNumCopies() + 1);
                    System.out.println("还书成功！");
                    return;
                }
            }
            System.out.println("未找到该书！");
        }
    }

    public static void main(String[] args) {
        ArrayList<Book> books = new ArrayList<>();
        books.add(new Book("Java编程思想", "Bruce Eckel", 2));
        books.add(new Book("Java核心技术", "Cay S. Horstmann", 3));
        Library library = new Library(books);

        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.println("请输入要执行的操作：");
            System.out.println("1. 添加图书");
            System.out.println("2. 删除图书");
            System.out.println("3. 显示所有图书");
            System.out.println("4. 借出图书");
            System.out.println("5. 归还图书");
            System.out.println("0. 退出程序");
            int choice = scanner.nextInt();
            scanner.nextLine(); // 处理掉输入缓冲区中的回车符

            switch (choice) {
                case 1:
                    System.out.println("请输入图书名称：");
                    String title = scanner.nextLine();
                    System.out.println("请输入作者名称：");
                    String author = scanner.nextLine();
                    System.out.println("请输入图书数量：");
                    int numCopies = scanner.nextInt();
                    scanner.nextLine(); // 处理掉输入缓冲区中的回车符
                    library.addBook(new Book(title, author, numCopies));
                    System.out.println("添加成功！");
                    break;

                case 2:
                    System.out.println("请输入要删除的图书名称：");
                    String titleToDelete = scanner.nextLine();
                    for (Book book : library.getBooks()) {
                        if (book.getTitle().equals(titleToDelete)) {
                            library.removeBook(book);
                            System.out.println("删除成功！");
                            break;
                        }
                    }
                    System.out.println("未找到该书！");
                    break;

                case 3:
                    library.displayBooks();
                    break;

                case 4:
                    System.out.println("请输入要借出的图书名称：");
                    String titleToBorrow = scanner.nextLine();
                    library.borrowBook(titleToBorrow);
                    break;

                case 5:
                    System.out.println("请输入要归还的图书名称：");
                    String titleToReturn = scanner.nextLine();
                    library.returnBook(titleToReturn);
                    break;

                case 0:
                    System.exit(0);

                default:
                    System.out.println("无效输入，请重新输入！");
                    break;
            }
        }
    }
}

这是一个简单的控制台程序，可以通过输入数字来选择不同的操作。其中，图书类和图书馆类都是内部类，可以根据需要进行修改和扩展。