题解 | #识别有效的IP地址和掩码并进行分类统计#

public class Main
{
    static final String FORMAT_STRING = "00000000"; 
    public static String addString(String src)
    {
    if (null == src) {
        return null;
    }
    int delta = FORMAT_STRING.length() - src.length();
    if (delta <= 0) {
        return src;
    }
    return FORMAT_STRING.substring(0, delta) + src;
    }
    
    
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        int numberA=0,numberB=0,numberC=0,numberD=0,numberE=0;
        int mistakeIP=0,mistakeMask=0;
        int privateIP=0;
        String handleIP,handleMask;
        while(sc.hasNext())
        {
            String input=sc.nextLine();
            handleIP=input.substring(0,input.indexOf("~"));
            handleMask=input.substring(input.indexOf("~")+1);
            String[] cutIP = handleIP.split("\\.");
            String[] cutMask = handleMask.split("\\.");
            String cutOne = Integer.toBinaryString( Integer.parseInt(cutMask[0]));
            String cuttwo = Integer.toBinaryString( Integer.parseInt(cutMask[1]));
            String cutthree = Integer.toBinaryString( Integer.parseInt(cutMask[2]));
            String cutfour = Integer.toBinaryString( Integer.parseInt(cutMask[3]));
            
            String together = addString(cutOne)+addString(cuttwo)+addString(cutthree)+addString(cutfour);
            if((together.indexOf("0")<=together.lastIndexOf("1"))
               &&Integer.parseInt(cutIP[0])!=0
               &&Integer.parseInt(cutIP[0])!=127)
            {
                mistakeMask++;
                cutIP[0]="-1";
            }
 
            for(int i=0;i<cutIP.length;i++)
            {
                if(cutIP[i].equals(""))
                    cutIP[0]="-1";
            }
            if((Integer.parseInt(cutIP[0])<127)&&(Integer.parseInt(cutIP[0])>0))
                {
                    if(Integer.parseInt(cutIP[0])==10)
                        privateIP++;
                    numberA++;
                }
                else if(Integer.parseInt(cutIP[0])<192&&Integer.parseInt(cutIP[0])>127)
                {
                    if(Integer.parseInt(cutIP[0])==172
                       &&Integer.parseInt(cutIP[1])>=16
                       &&Integer.parseInt(cutIP[1])<=31)
                        privateIP++;
                    numberB++;
                }
                else if(Integer.parseInt(cutIP[0])<224&&Integer.parseInt(cutIP[0])>191)
                {
                    if(Integer.parseInt(cutIP[0])==192
                       &&Integer.parseInt(cutIP[1])==168)
                        privateIP++;
                    numberC++;
                }
                else if(Integer.parseInt(cutIP[0])<240&&Integer.parseInt(cutIP[0])>223)
                    numberD++;
                else if(Integer.parseInt(cutIP[0])<256&&Integer.parseInt(cutIP[0])>239)
                    numberE++;
                else if(Integer.parseInt(cutIP[0])==0||Integer.parseInt(cutIP[0])==127)
                    continue;
                else
                {
                     mistakeIP++;
                }

        }
        int abc = mistakeMask+mistakeIP;
        System.out.print(numberA+" "+numberB+" "+numberC+" "+numberD
                        +" "+numberE+" "+mistakeIP+" "+privateIP);
   }
}