Java：完成对用户表 的增删改查 用户表字段 ID username password

好的，我可以为您提供Java代码来完成对用户表的增删改查操作。需要注意的是，这里假设您已经有了一个数据库连接对象conn，以及一个User类，其中包含了ID、username和password字段的定义。

1. 增加用户

public void addUser(User user) {
    try {
        String sql = "INSERT INTO user (username, password) VALUES (?, ?)";
        PreparedStatement statement = conn.prepareStatement(sql);
        statement.setString(1, user.getUsername());
        statement.setString(2, user.getPassword());
        statement.executeUpdate();
        statement.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

2. 删除用户

public void deleteUser(int id) {
    try {
        String sql = "DELETE FROM user WHERE id=?";
        PreparedStatement statement = conn.prepareStatement(sql);
        statement.setInt(1, id);
        statement.executeUpdate();
        statement.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

3. 修改用户

public void updateUser(User user) {
    try {
        String sql = "UPDATE user SET username=?, password=? WHERE id=?";
        PreparedStatement statement = conn.prepareStatement(sql);
        statement.setString(1, user.getUsername());
        statement.setString(2, user.getPassword());
        statement.setInt(3, user.getId());
        statement.executeUpdate();
        statement.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

4. 查询用户

public User getUserById(int id) {
    User user = null;
    try {
        String sql = "SELECT * FROM user WHERE id=?";
        PreparedStatement statement = conn.prepareStatement(sql);
        statement.setInt(1, id);
        ResultSet resultSet = statement.executeQuery();
        if (resultSet.next()) {
            user = new User();
            user.setId(resultSet.getInt("id"));
            user.setUsername(resultSet.getString("username"));
            user.setPassword(resultSet.getString("password"));
        }
        resultSet.close();
        statement.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return user;
}

以上就是Java代码实现对用户表进行增删改查操作的示例，希望对您有所帮助。