/*
  * This program first judge whether a decimal number is entered,
  * then convert a decimal number
  * to two's complement representation, then covert two's complement representation
  *  to four digits hexadecimal number. Last print out two ASCII characters
  */

 public class Convert
 {
    public static void main (String[] args)
    {
     System.out.println();
     System.out.println("Please enter a number.");
     System.out.println();
     String inPutString,newString,junk;
     int lengthOfString,i,j;
     int m=0,integer=0,integerNumber=0;
     int lengthOfNewString;
     inPutString=SavitchIn.readLine();  // input a string from keyboard
     System.out.println();
     System.out.println ("The string you entered is "+inPutString);
     System.out.println();
     lengthOfString=inPutString.length();  // find  the length of the string entered
     int[] factor=new int[lengthOfString];
     int[] number=new int[lengthOfString];
     for (i=0;i<=lengthOfString-1;i++)
          {
          number[i]=0;
          }
     for (i=0; i<=lengthOfString-1; i++)
        {
         factor[i]=0;
        }
     /*
      * To find whether the first character of inPutString is '-'
      * If inPutString conatin a '-', then define a newString
      * which is the same as inPutString except that newString
      * do not contain '-'. This is for convert a negative decimal nuber to
      * binary. After conversion is completed, this progarm will add 1 to
      * the most siganificant bit. So this will confirm that the number is negative
      */
     if (inPutString.charAt(0)!='-')   newString=inPutString;
     else
          {
          newString=inPutString.substring(1,lengthOfString);
          }
     /*
      * Judge whether the whether the inPutString is a decimal number
      */
     lengthOfNewString=newString.length(); // positive number or negavive number without '-'
     for (j=0; j<=lengthOfNewString-1; j++)
             {
              if (newString.charAt(j)=='0') factor[j]=1;
              else if (newString.charAt(j)=='1') factor[j]=1;
              else if (newString.charAt(j)=='2') factor[j]=1;
              else if (newString.charAt(j)=='3') factor[j]=1;
              else if (newString.charAt(j)=='4') factor[j]=1;
              else if (newString.charAt(j)=='5') factor[j]=1;
              else if (newString.charAt(j)=='6') factor[j]=1;
              else if (newString.charAt(j)=='7') factor[j]=1;
              else if (newString.charAt(j)=='8') factor[j]=1;
              else if (newString.charAt(j)=='9') factor[j]=1;
              m=m+factor[j];
             }
          if (m!=lengthOfNewString)
             {
              System.out.println("Sorry,the String you entered is not an integer.");
              System.out.println("Please try again.");
              System.out.println("Press enter key to continue.");
              junk=SavitchIn.readLine();
              System.exit(0);
             }
       // Convert the string to decimal number
       for (j=0;j<=lengthOfNewString-1;j++)
           {
            if (newString.charAt(j)=='1') number[j]=1;
            else if (newString.charAt(j)=='1') number[j]=1;
            else if (newString.charAt(j)=='2') number[j]=2;
            else if (newString.charAt(j)=='3') number[j]=3;
            else if (newString.charAt(j)=='4') number[j]=4;
            else if (newString.charAt(j)=='5') number[j]=5;
            else if (newString.charAt(j)=='6') number[j]=6;
            else if (newString.charAt(j)=='7') number[j]=7;
            else if (newString.charAt(j)=='8') number[j]=8;
            else if (newString.charAt(j)=='9') number[j]=9;
            else if (newString.charAt(j)=='0') number[j]=0;
            }
        for (j=0;j<=lengthOfNewString-1;j++)
            {
             integerNumber=integerNumber+number[j]*(int)Math.pow(10,(lengthOfNewString-j-1));
             }
        if (lengthOfString!=lengthOfNewString) integerNumber=-integerNumber; // restore '-'
                                                                       // to negative number
        if (integerNumber<-32768)  // set boundary
           {
            System.out.println("The integer you entered is too small.");
            System.out.println("It should be between -32768 to 32767.");
            System.out.println("Press enter key to continue");
            junk=SavitchIn.readLine();
            System.exit(0);
           }
          if (integerNumber>32767)   // set boundary
           {
            System.out.println("The integer you entered is too large.");
            System.out.println("It should be between -32768 to 32767.");
            System.out.println("Press enter key to continue");
            junk=SavitchIn.readLine();
            System.exit(0);
            }

       /*
        * begin to convert decimal number to binary
        */
        int integerFactor;
        integerFactor=integerNumber;
        if (integerNumber<0) integerNumber=-integerNumber;
        if (integerNumber==32768)  integerNumber=0;
        int[] bin=new int[16]; //define an array to contain 16 binary digits
        for (i=0;i<=15;i++)
            {
            bin[i]=0;
            }
         for (i=15;i>=1;i--)   // convert to binary
             {
             bin[i]=integerNumber%2;
             integerNumber=integerNumber/2;
             }
         if (lengthOfString!=lengthOfNewString) //convert to one's complement represention
             {
             for (i=0;i<=15;i++)
                 {
                 if (bin[i]==1) bin[i]=0;
                 else bin[i]=1;
                 }
             }
      /*
       * Convert to two's complement representation
       */
          int[] data=new int[16]; // array data reserve original digitss
          for (i=0;i<=15;i++)     // to use to judge whether there is an
             {                    // change from 1 to 0 in the next loop
              data[i]=bin[i];
              }
          if (lengthOfString!=lengthOfNewString)
             {
              if (bin[15]==0) bin[15]=1;
              else
                  {
                   bin[15]=0;
                   for(i=14;i>=0;i--)
                      {
                      if (bin[i]==1&&data[i+1]==1) bin[i]=0;
                      else if (bin[i]==1&&data[i+1]==0)
                          {
                           bin[i]=1;
                           break;
                          }
                      else if (bin[i]==0)
                          {
                          bin[i]=1;
                          break;
                           }
                      }
                  }
             }
       if (integerFactor==-32768)   // -32768 is special number, so consider it separately
           {
            bin[0]=1;
            for (i=1;i<=15;i++)
                {
                bin[i]=0;
                 }
            }
          System.out.println("The two's complement representation of "+integerFactor+" is:");
          System.out.println();
          for (i=0;i<=15;i++)
                {
                System.out.print(bin[i]);
                }
          System.out.println();
         /*
          * convert to hexadecimal number
          *
          */
          char[] hex=new char[5];
          for(i=1;i<=4;i++)
              {
              hex[i]='0';
               }
           for(i=15;i>=3;i=i-4)
              {
              if (bin[i-3]==0&bin[i-2]==0&bin[i-1]==0&bin[i]==0) hex[(i+1)/4]='0';
              if (bin[i-3]==0&bin[i-2]==0&bin[i-1]==0&bin[i]==1) hex[(i+1)/4]='1';
              if (bin[i-3]==0&bin[i-2]==0&bin[i-1]==1&bin[i]==0) hex[(i+1)/4]='2';
              if (bin[i-3]==0&bin[i-2]==0&bin[i-1]==1&bin[i]==1) hex[(i+1)/4]='3';
              if (bin[i-3]==0&bin[i-2]==1&bin[i-1]==0&bin[i]==0) hex[(i+1)/4]='4';
              if (bin[i-3]==0&bin[i-2]==1&bin[i-1]==0&bin[i]==1) hex[(i+1)/4]='5';
              if (bin[i-3]==0&bin[i-2]==1&bin[i-1]==1&bin[i]==0) hex[(i+1)/4]='6';
              if (bin[i-3]==0&bin[i-2]==1&bin[i-1]==1&bin[i]==1) hex[(i+1)/4]='7';
              if (bin[i-3]==1&bin[i-2]==0&bin[i-1]==0&bin[i]==0) hex[(i+1)/4]='8';
              if (bin[i-3]==1&bin[i-2]==0&bin[i-1]==0&bin[i]==1) hex[(i+1)/4]='9';
              if (bin[i-3]==1&bin[i-2]==0&bin[i-1]==1&bin[i]==0) hex[(i+1)/4]='A';
              if (bin[i-3]==1&bin[i-2]==0&bin[i-1]==1&bin[i]==1) hex[(i+1)/4]='B';
              if (bin[i-3]==1&bin[i-2]==1&bin[i-1]==0&bin[i]==0) hex[(i+1)/4]='C';
              if (bin[i-3]==1&bin[i-2]==1&bin[i-1]==0&bin[i]==1) hex[(i+1)/4]='D';
              if (bin[i-3]==1&bin[i-2]==1&bin[i-1]==1&bin[i]==0) hex[(i+1)/4]='E';
              if (bin[i-3]==1&bin[i-2]==1&bin[i-1]==1&bin[i]==1) hex[(i+1)/4]='F';
              }
            System.out.println();
            System.out.println("The hexademical of "+integerFactor+" is:");
            System.out.println();
            System.out.print(hex[1]);
            System.out.print(hex[2]);
            System.out.print(hex[3]);
            System.out.print(hex[4]);
            System.out.println();
           /*
            * to convert two's representation to ASCII
            */
             char ascii1,ascii2;
             int number2=bin[9]*(int)Math.pow(2,6)+bin[10]*(int)Math.pow(2,5)+bin[11]*(int)Math.pow(2,4)+bin[12]*(int)Math.pow(2,3)+bin[13]*(int)Math.pow(2,2)+bin[14]*2+bin[15];
             int number1=bin[1]*(int)Math.pow(2,6)+bin[2]*(int)Math.pow(2,5)+bin[3]*(int)Math.pow(2,4)+bin[4]*(int)Math.pow(2,3)+bin[5]*(int)Math.pow(2,2)+bin[6]*2+bin[7];
             if (number1<32||number1>126)
                {
                System.out.println("Sorry,the first ASCII character is unprintable.");
                System.out.println(" ");
                 }
             else
                 {
                 ascii1=(char)number1;
                 System.out.println("The first ASCII characters is:");
                 System.out.println(ascii1);
                 }
            if (number2<32||number2>126)
               {
                System.out.println("Sorry,the second ASCII character is unprintable.");
                System.out.println(" ");
               }
             else
                {
                 ascii2=(char)number2;
                 System.out.println("The second ASCII characters is:");
                 System.out.println(ascii2);
                 }

    }
}