Converting a numeric string to a number (Java)

1 //The parseint method and the character.digit are not allowed when the numeric string is converted to a numeric type (the legitimacy of the input string is not considered here)2  Public classConvertnumstr {3      Public Static voidMain (string[] args) {4System.out.print (Convertstr2num ("-2015")));5     }6      Public Static intconvertstr2num (String str) {7         intLength=str.length ();8         intResult=0;9         intI=length-1;Ten          One          while(i>0) { A             CharC=Str.charat (i); -             intnum=c-' 0 ';//the corresponding character number, converted to a digital -Result+=num*math.pow (length-i-1); thei--; -         } -         if(Str.charat (0) = = '-') { -             return0-result; +}Else { -             return(int) (Result+ (Str.charat (i)-' 0 ') *math.pow (length-i-1)); +         } A     } at}

Converting a numeric string to a number (Java)