一隻檢查 IP 和 Hostname 格式的 JAVA 小程式

還是那句老話，我不喜歡JAVA。那這篇文章怎麼會存在呢？因為要解決同事開發Android軟體上所遇到的問題，所以不得不跳下來寫。

import java.util.regex.*;

public class CheckIPHostName 
{
    public static void main(String[] args) 
    {
        String    input;
        
        if (args.length > 0)
        {
            input = args[0];
        }
        else 
        {
            // No input was given.  Print a message and exit.
            System.out.println("Usage:  java DateClient <server_host_name>");
            return;
        }
        
        Pattern IpPattern = Pattern.compile( "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\\.){3}
                        ([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$" );
        Pattern HostPattern = Pattern.compile( "^(([a-zA-Z]|[a-zA-Z][a-zA-Z0-9\\-]*[a-zA-Z0-9])\\.)*
                        ([A-Za-z]|[A-Za-z][A-Za-z0-9\\-]*[A-Za-z0-9])$" );
        
        Matcher matcherIp = IpPattern.matcher( input );
        Matcher matcherHost = HostPattern.matcher( input );
        
        if( matcherIp.matches() )
        {
            System.out.printf( "%s is an IP address.\n", input );
        }
        else if( matcherHost.matches() )
        {
            System.out.printf( "%s is a host name.\n", input );
        }
        else
        {
            System.out.printf( "%s is invalid.\n", input );
        }
        
        return;                           
    }
}