数字字符串转数值

public int digitToValue(char c){    if(c>='0' && c<='9')         return c-'0';    else if(c>='A' && c<='Z')         return 10+c-'A';    else if(c>='a' && c<='z')         return 10+c-'z';    return -1;}public int convertToBase(String number, int base){    if(base<2 || (base>10 && base!=16))         return -1;    int value=0;    for(int i=number.length()-1; i>=0; i--){        int digit = digitToValue(number.charAt(i));        if(digit<0||digit>=base)            return -1;        int exp = number.length()-1-i;        value += digit*Math.pow(base, exp);    }    return value;}