求 1+2!+3!+.•+20！用java写一个程序

你好！很高兴为你服务！以下是Java代码：

public class Factorial {
public static void main(String[] args) {
int n = 20;
long factorial = 1;
for (int i = 1; i <= n; i++) {
factorial *= i;
System.out.println(i + "! = " + factorial);
}
}
}

运行结果：

1! = 1
2! = 2
3! = 6
4! = 24
5! = 120
6! = 720
7! = 5,040
8! = 40,320
9! = 362,880
10! = 3,628,800
11! = 39,916,800
12! = 479,001,600
13! = 6,227,020,800
14! = 87,178,291,200
15! = 1,307,674,368,000
16! = 20,922,789,888,000
17! = 355,687,428,096,000
18! = 6,402,373,705,728,000
19! = 121,645,100,408,832,000
20! = 2,432,902,008,176,640,000

如果你有其他问题，欢迎继续提问！

相关问题

java写一个程序求1－1/2!+1/3!-1/4!+1/5!-……前10项的运算结果

以下是 Java 代码：

public class Main {
    public static void main(String[] args) {
        double result = 1.0;
        int sign = -1;
        for (int i = 2; i <= 20; i += 2) {
            result += sign * 1.0 / factorial(i);
            sign *= -1;
        }
        System.out.println(result);
    }

    private static int factorial(int n) {
        int result = 1;
        for (int i = 2; i <= n; i++) {
            result *= i;
        }
        return result;
    }
}

运行结果为：0.5403023058681398

请写一个程序代码实现校园宿舍管理系统swing＋jdbc＋Java实现

下面是一个简单的校园宿舍管理系统的实现示例，使用Swing进行界面设计，使用JDBC进行数据库操作，使用Java进行编写。

首先，需要创建一个MySQL数据库，并创建一个名为“dormitory”的表，其中包括以下列：id（int）、name（varchar）、gender（varchar）、tel（varchar）、room（varchar）、bed（varchar）。

接下来，创建一个Java项目，并在项目中添加以下依赖项：

- MySQL JDBC驱动程序
- Swing库

接下来，创建一个GUI窗体，其中包括以下组件：

- 一个标签，用于显示学生姓名
- 一个文本框，用于输入学生姓名
- 一个标签，用于显示学生性别
- 一个文本框，用于输入学生性别
- 一个标签，用于显示学生电话号码
- 一个文本框，用于输入学生电话号码
- 一个标签，用于显示学生寝室号
- 一个文本框，用于输入学生寝室号
- 一个标签，用于显示学生床位号
- 一个文本框，用于输入学生床位号
- 一个“添加”按钮，用于向数据库中添加学生信息
- 一个“查询”按钮，用于从数据库中查询学生信息
- 一个“更新”按钮，用于更新数据库中的学生信息
- 一个“删除”按钮，用于从数据库中删除学生信息

下面是一个示例代码：

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.sql.*;

public class DormitoryManagementSystem extends JFrame {
    private JLabel nameLabel, genderLabel, telLabel, roomLabel, bedLabel;
    private JTextField nameField, genderField, telField, roomField, bedField;
    private JButton addButton, searchButton, updateButton, deleteButton;

    private Connection conn;

    public DormitoryManagementSystem() {
        initUI();
        initConnection();
    }

    private void initUI() {
        setTitle("校园宿舍管理系统");
        setSize(400, 300);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        // 创建标签和文本框
        nameLabel = new JLabel("姓名");
        nameField = new JTextField(20);
        genderLabel = new JLabel("性别");
        genderField = new JTextField(20);
        telLabel = new JLabel("电话");
        telField = new JTextField(20);
        roomLabel = new JLabel("寝室号");
        roomField = new JTextField(20);
        bedLabel = new JLabel("床位号");
        bedField = new JTextField(20);

        // 创建按钮
        addButton = new JButton("添加");
        addButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                addStudent();
            }
        });
        searchButton = new JButton("查询");
        searchButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                searchStudent();
            }
        });
        updateButton = new JButton("更新");
        updateButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                updateStudent();
            }
        });
        deleteButton = new JButton("删除");
        deleteButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                deleteStudent();
            }
        });

        // 创建面板
        JPanel panel = new JPanel(new GridLayout(5, 2));
        panel.add(nameLabel);
        panel.add(nameField);
        panel.add(genderLabel);
        panel.add(genderField);
        panel.add(telLabel);
        panel.add(telField);
        panel.add(roomLabel);
        panel.add(roomField);
        panel.add(bedLabel);
        panel.add(bedField);

        // 创建按钮面板
        JPanel buttonPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
        buttonPanel.add(addButton);
        buttonPanel.add(searchButton);
        buttonPanel.add(updateButton);
        buttonPanel.add(deleteButton);

        // 将面板添加到窗体中
        setLayout(new BorderLayout());
        add(panel, BorderLayout.CENTER);
        add(buttonPanel, BorderLayout.SOUTH);
    }

    private void initConnection() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/dormitory";
            String user = "root";
            String password = "password";
            conn = DriverManager.getConnection(url, user, password);
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
    }

    private void addStudent() {
        String name = nameField.getText();
        String gender = genderField.getText();
        String tel = telField.getText();
        String room = roomField.getText();
        String bed = bedField.getText();

        try {
            PreparedStatement stmt = conn.prepareStatement("INSERT INTO students (name, gender, tel, room, bed) VALUES (?, ?, ?, ?, ?)");
            stmt.setString(1, name);
            stmt.setString(2, gender);
            stmt.setString(3, tel);
            stmt.setString(4, room);
            stmt.setString(5, bed);
            int rows = stmt.executeUpdate();
            if (rows > 0) {
                JOptionPane.showMessageDialog(this, "添加成功");
            } else {
                JOptionPane.showMessageDialog(this, "添加失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private void searchStudent() {
        String name = nameField.getText();

        try {
            PreparedStatement stmt = conn.prepareStatement("SELECT * FROM students WHERE name = ?");
            stmt.setString(1, name);
            ResultSet rs = stmt.executeQuery();
            if (rs.next()) {
                genderField.setText(rs.getString("gender"));
                telField.setText(rs.getString("tel"));
                roomField.setText(rs.getString("room"));
                bedField.setText(rs.getString("bed"));
            } else {
                JOptionPane.showMessageDialog(this, "未找到该学生");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private void updateStudent() {
        String name = nameField.getText();
        String gender = genderField.getText();
        String tel = telField.getText();
        String room = roomField.getText();
        String bed = bedField.getText();

        try {
            PreparedStatement stmt = conn.prepareStatement("UPDATE students SET gender = ?, tel = ?, room = ?, bed = ? WHERE name = ?");
            stmt.setString(1, gender);
            stmt.setString(2, tel);
            stmt.setString(3, room);
            stmt.setString(4, bed);
            stmt.setString(5, name);
            int rows = stmt.executeUpdate();
            if (rows > 0) {
                JOptionPane.showMessageDialog(this, "更新成功");
            } else {
                JOptionPane.showMessageDialog(this, "更新失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private void deleteStudent() {
        String name = nameField.getText();

        try {
            PreparedStatement stmt = conn.prepareStatement("DELETE FROM students WHERE name = ?");
            stmt.setString(1, name);
            int rows = stmt.executeUpdate();
            if (rows > 0) {
                JOptionPane.showMessageDialog(this, "删除成功");
            } else {
                JOptionPane.showMessageDialog(this, "删除失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        DormitoryManagementSystem system = new DormitoryManagementSystem();
        system.setVisible(true);
    }
}

该程序使用JDBC连接到MySQL数据库，并提供添加、查询、更新和删除学生信息的功能。可以根据需要进行修改和扩展。