这是Java练手的一个小项目，适合初学者，用的技术是Java和MySQL。主要功能包括
（1）用户登录
（2）增加图书
（3）修改图书信息
（4）删除图书信息
（5）查询图书
（6）查看所有的图书

下面是源码

public class BookManager{
	LinkedHashMap<String, Book> stu = new LinkedHashMap<String, Book>();
	Book book = new Book();
	Scanner sc = new Scanner(System.in);
		
	public void Manage(int choice) throws Exception{			
		switch (choice) {
			case 0:
				list();
				break;
			case 1:
				find();
				break;
			case 2:
				add();
				break;
			case 3:
				modify();
				break;
			case 4:
				delete();
				break;
			default: {
				throw new Exception("没有该功能，请重新选择！");
			}		
		}		
	}
	
	//获取所有书籍
	public void list() {
		Dao dao = new Dao();
		List<Book> list = dao.getAllBooks();
		System.out.println("书籍列表如下：");
		for(Book book : list) {
			System.out.println("书名："+book.getName()+" 作者："+book.getAuthor()+" 库存量："+book.getNum());
		}	
	}
		
	//搜索书籍
	public void find() {
		System.out.println("输入要搜索的书名：");
		String name = sc.next();
		Dao dao = new Dao();
		if(!dao.judgeExist(name))
			System.out.println("该书籍不存在！");
		else{
			Book book = dao.find(name);
			System.out.println("书名："+book.getName()+" 作者："+book.getAuthor()+" 库存量："+book.getNum());
		}
	}
	
	//添加书籍
	public void add() {
		Dao dao = new Dao();
		System.out.println("输入要添加的书名：");
		String name = sc.next();
		if(dao.judgeExist(name))
			System.out.println("该书籍已存在！");
		else{
			System.out.println("输入作者：");
			String author = sc.next();
			System.out.println("输入数量：");
			int num = sc.nextInt();
			dao.addBook(new Book(name,author,num));
			System.out.println("添加成功！");
			list();
		}
	}
 
	//修改书籍
	public void modify(){
		System.out.println("输入要修改的书名：");
		String name = sc.next();
		Dao dao = new Dao();
		if(!dao.judgeExist(name))
			System.out.println("该书籍不存在！");
		else{
			Book book = dao.find(name);
			System.out.println("书名："+book.getName()+" 作者："+book.getAuthor()+" 库存量："+book.getNum());
			System.out.println("输入修改后的书名：");
			String newname = sc.next();
			System.out.println("输入修改后的作者：");
			String newauthor = sc.next();
			System.out.println("输入修改后的库存量：");
			int newnum = sc.nextInt();
			dao.modifyBook(name, new Book(newname,newauthor,newnum));
			System.out.println("修改成功！");
		}
	}
 
	//删除书籍
	public void delete() {
		System.out.println("请输入要删除的书名：");
		String name = sc.next();
		Dao dao = new Dao();
		if(!dao.judgeExist(name)) {
			System.out.println("书籍不存在！");
		}
		else{ 
			dao.deleteBook(name);
			System.out.println("删除成功！");
		}
	}
}

BookManager主要是和用户进行交互，在控制台显示信息提示用户如何操作，并且调用dao查询数据库拿到结果返回给用户。

public class Dao {
	
	/**
	 * 根据书名判定书籍是否已存在
	 */
	public boolean judgeExist(String targetName){
	Connection conn = null; 
	PreparedStatement stmt = null;	
	ResultSet rs = null;
	int count = 0;
	try {
		conn = MySQLUtils.getConn();
		String sql = "select count(*) as count from book where book_name = ?";
		stmt = conn.prepareStatement(sql);
		stmt.setString(1, targetName);
		rs = stmt.executeQuery();
		while(rs.next()){
			count = rs.getInt("count");
		}
	} 
	catch (SQLException e) {
		e.printStackTrace();
	}
	finally{
		MySQLUtils.closeConn(conn, stmt, rs);
	}
	if(count==0) return false;
	else
		return true;
   }
	
	
	/**
	 * 获取所有书籍列表
	 */
	public List<Book> getAllBooks(){
		Connection conn = null; 
		Statement stmt = null;	
		ResultSet rs = null;
		List<Book> bookList = new ArrayList<>();
		try {
			
			conn = MySQLUtils.getConn();
			String sql = "select * from book";
			stmt = conn.createStatement();
			rs = stmt.executeQuery(sql);
			while(rs.next()){
				String name = rs.getString("book_name");
				String author = rs.getString("book_author");
				int num = rs.getInt("book_num");
				Book book = new Book(name, author, num);
				bookList.add(book);
			}
		} 
		catch (SQLException e) {
			e.printStackTrace();
		}
		finally{
			MySQLUtils.closeConn(conn, stmt, rs);
		}
		return bookList;
	}
	
	/**
	 * 根据书名查找书籍详细信息
	 */
	public Book find(String bookName){
		Connection conn = null; 
		PreparedStatement stmt = null;	
		Book book = null;
		try {
			conn = MySQLUtils.getConn();
			String sql = "select * from book where book_name = ?";
			stmt = conn.prepareStatement(sql);
			stmt.setString(1, bookName);
			ResultSet tmpres = stmt.executeQuery();
			book = new Book();
			while(tmpres.next()){
				book.setName(tmpres.getString("book_name"));
				book.setAuthor(tmpres.getString("book_author"));
				book.setNum(tmpres.getInt("book_num"));
			}
		} 
		catch (SQLException e) {
			e.printStackTrace();
		}
		finally{
			MySQLUtils.closeConn(conn, stmt);
		}
		return book;
	}
	
	/**
	 * 添书
	 */
	public void addBook(Book book){
		Connection conn = null; 
		PreparedStatement stmt = null;	
		try {
			conn = MySQLUtils.getConn();
			String sql = "insert into book(book_name, book_author, book_num) values(?,?,?)";
			stmt = conn.prepareStatement(sql);
			stmt.setString(1, book.getName());
			stmt.setString(2, book.getAuthor());
			stmt.setInt(3, book.getNum());
			stmt.executeUpdate();
		} 
		catch (SQLException e) {
			e.printStackTrace();
		}
		finally{
			MySQLUtils.closeConn(conn, stmt);
		}
	}
	
	/**
	 * 修改书
	 */
	public void modifyBook(String targetName, Book book){
		Connection conn = null;
		PreparedStatement stmt = null;
		try {
			conn = MySQLUtils.getConn();
			String sql = "update book set book_name = ?, book_author = ?,  book_num = ? where book_name = ?";
			stmt = conn.prepareStatement(sql);
			stmt.setString(1, book.getName());
			stmt.setString(2, book.getAuthor());
			stmt.setInt(3, book.getNum());
			stmt.setString(4, targetName);
			stmt.executeUpdate();
		}
		catch (SQLException e) {
			e.printStackTrace();
		}
		finally{
			MySQLUtils.closeConn(conn, stmt);
		}
	}
	
	/**
	 * 删书
	 */
	public void deleteBook(String bookName){
		Connection conn = null; 
		PreparedStatement stmt = null;	
		try {
			conn = MySQLUtils.getConn();
			String sql = "delete from book where book_name = ?";
			stmt = conn.prepareStatement(sql);
			stmt.setString(1, bookName);
			stmt.executeUpdate();
		} 
		catch (SQLException e) {
			e.printStackTrace();
		}
		finally{
			MySQLUtils.closeConn(conn, stmt);
		}
	}
}

Dao类就是和数据库交互，执行sql语句从数据库取得结果。

下面是运行界面

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