public class Test { public static void main(String[] args) { int a = 0; while (a < 10) { switch (a) { case 0: case 1: case 2:a = a + 2; break; case 3: a = a + 3; default:a = a + 5; } } System.out.print(a);}}

这段代码的输出结果是20。

代码中定义了一个整型变量a并初始化为0，然后进入while循环。在while循环中，通过switch语句根据a的值选择不同的分支。当a的值为0、1或2时，a会加2；当a的值为3时，a会加3；否则，a会加5。每次执行完switch语句后，a的值会被更新，直到a的值大于等于10时，while循环结束。最后，打印出a的值，即20。

相关问题

下列程序运行后输出的结果是 public class Test { public static void main(String{] args) int a = 0; while (a < 10) ‹ switch (a) f case O: case 1: a = a + 2: case 2: case 3: a = a + 3; break; default:a = a + 5;

这段代码是无法通过编译的，因为其中有多处语法错误。下面是修正后的代码：

public class Test {
    public static void main(String[] args) {
        int a = 0;
        while (a < 10) {
            switch (a) {
                case 0:
                case 1:
                    a = a + 2;
                    break;
                case 2:
                case 3:
                    a = a + 3;
                    break;
                default:
                    a = a + 5;
                    break;
            }
        }
        System.out.println(a);
    }
}

上述代码的输出结果是 15。

package data3; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLDataException; import java.sql.SQLException; import java.text.ParseException; import java.util.ArrayList; import java.util.Date; import java.util.List; import java.util.Scanner; import data3.test.classselect; public class main { private static List<tele> telelist=new ArrayList<tele>(); public static void main(String[] args) throws ClassNotFoundException, SQLException { Scanner scanner = new Scanner(System.in); int choice; while (true) { displayMenu(); choice = scanner.nextInt(); scanner.nextLine(); // 清除输入缓冲区中的换行符 switch (choice) { case 1: showUserList(); break; case 2: update(); break; case 3: Insert(); break; case 4: delete(); break; case 0: System.out.println("感谢使用！"); return; default: System.out.println("无效的选项，请重新输入。"); } } } private static void displayMenu() { System.out.println("------------------手机营销充值中心----------------"); System.out.print("1. 查看手机用户列表"); System.out.print(" 2. 充值"); System.out.print(" 3. 新用户注册"); System.out.print(" 4. 老用户注销"); System.out.println(" 0. 退出"); System.out.print("请选择操作："); } private static List<tele> showUserList() throws SQLException { Connection conn=null; PreparedStatement pst =null; ResultSet rs =null; try { conn = classselect.getConnection(); String sql = "select * from phone"; pst = conn.prepareStatement(sql); rs = pst.executeQuery(); List<tele；；这是一串代码，请帮我完善

telelist = new ArrayList<tele>(); // 创建手机用户列表 while (rs.next()) { // 遍历结果集并将每个用户添加到列表中 int id = rs.getInt(1); String name = rs.getString(2); String gender = rs.getString(3); String phone = rs.getString(4); int balance = rs.getInt(5); telelist.add(new tele(id, name, gender, phone, balance)); } System.out.println("手机用户列表："); System.out.println("编号\t姓名\t性别\t手机号码\t余额"); for (tele t : telelist) { // 遍历用户列表并输出用户信息 System.out.println(t.getId() + "\t" + t.getName() + "\t" + t.getGender() + "\t" + t.getPhone() + "\t" + t.getBalance()); } return telelist; } catch (SQLException e) { e.printStackTrace(); } finally { rs.close(); pst.close(); conn.close(); } return null; } private static void update() throws SQLException { Scanner scanner = new Scanner(System.in); System.out.print("请输入要充值的手机号码："); String phone = scanner.next(); System.out.print("请输入充值金额："); int amount = scanner.nextInt(); Connection conn=null; PreparedStatement pst =null; ResultSet rs =null; try { conn = classselect.getConnection(); String sql = "update phone set balance=balance+? where phone=?"; pst = conn.prepareStatement(sql); pst.setInt(1, amount); pst.setString(2, phone); int rows = pst.executeUpdate(); if (rows > 0) { System.out.println("充值成功！"); } else { System.out.println("充值失败，请检查手机号码是否正确。"); } } catch (SQLException e) { e.printStackTrace(); } finally { rs.close(); pst.close(); conn.close(); } } private static void Insert() throws SQLException { Scanner scanner = new Scanner(System.in); System.out.print("请输入姓名："); String name = scanner.next(); System.out.print("请输入性别："); String gender = scanner.next(); System.out.print("请输入手机号码："); String phone = scanner.next(); System.out.print("请输入初始余额："); int balance = scanner.nextInt(); Connection conn=null; PreparedStatement pst =null; ResultSet rs =null; try { conn = classselect.getConnection(); String sql = "insert into phone(name,gender,phone,balance) values(?,?,?,?)"; pst = conn.prepareStatement(sql); pst.setString(1, name); pst.setString(2, gender); pst.setString(3, phone); pst.setInt(4, balance); int rows = pst.executeUpdate(); if (rows > 0) { System.out.println("注册成功！"); } else { System.out.println("注册失败，请检查手机号码是否已注册。"); } } catch (SQLException e) { e.printStackTrace(); } finally { rs.close(); pst.close(); conn.close(); } } private static void delete() throws SQLException { Scanner scanner = new Scanner(System.in); System.out.print("请输入要注销的手机号码："); String phone = scanner.next(); Connection conn=null; PreparedStatement pst =null; ResultSet rs =null; try { conn = classselect.getConnection(); String sql = "delete from phone where phone=?"; pst = conn.prepareStatement(sql); pst.setString(1, phone); int rows = pst.executeUpdate(); if (rows > 0) { System.out.println("注销成功！"); } else { System.out.println("注销失败，请检查手机号码是否正确。"); } } catch (SQLException e) { e.printStackTrace(); } finally { rs.close(); pst.close(); conn.close(); } }