Question

我想在Tcl中检查输入是否是有效数字。即：
1.2.0不是。
1.20是。
1e-9是-00.61是。
1.91e-a0不是。
我在网上找不到一个好的答案。

Answer 1

package Beans;  

import java.io.*;  
import java.sql.*;  
import javax.servlet.ServletException;  
import javax.servlet.http.*;  

public class CheckAvailability extends HttpServlet {  

 private static final long serialVersionUID = -734503860925086969L;  

 @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  
        doPost(request, response);  
    }  

 @Override
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  


        response.setContentType("text/html;charset=UTF-8");  
        PrintWriter out = response.getWriter();  

        try {  

            String connectionURL = "jdbc:mysql://localhost:3306/teddb"; // teddb is my database name  
            Connection connection;  
            Class.forName("com.mysql.jdbc.Driver").newInstance();  
            connection = DriverManager.getConnection(connectionURL, "root", "Sk1994!!");  


            String uname = request.getParameter("name");  

            PreparedStatement ps = connection.prepareStatement("select username from users where username=?");  
            ps.setString(1,uname);  
            ResultSet rs = ps.executeQuery();  

            if (!rs.next()) {  
                out.println("");  
            }  
            else{  
                out.println("Username already in use");  
            }  
            out.println();  

        } 
        catch (ClassNotFoundException | InstantiationException | IllegalAccessException | SQLException ex) {  
            out.println("Error ->" + ex.getMessage());  
        } finally {  
            out.close();  
        }  
    }  
}

如果它是有效数字，则返回1，否则返回0.请注意，除非您提供string is double $myNum选项，否则空字符串将被视为有效数字：

-strict

文档：string

如何判断变量值是否为TCL中的数字？

1 个答案: