ModStrings.java

package mmc.utils.strings;

import org.jetbrains.annotations.*;

public class ModStrings{
    public static boolean canParseLong(String s){
        return parseLong(s)!=null;
    }
    @Nullable
    public static Long parseLong(String s){
        return parseLong(s, 10);
    }

    @Nullable
    public static Long parseLong(String s, int radix){
        return parseLong(s, radix, 0, s.length());
    }

    @Nullable
    public static Long parseLong(String s, int radix, int start, int end){
        boolean negative = false;
        int i = start, len = end - start;
        long limit = -9223372036854775807L;
        if(len <= 0){
            return null;
        }else{
            char firstChar = s.charAt(i);
            if(firstChar < '0'){
                if(firstChar == '-'){
                    negative = true;
                    limit = -9223372036854775808L;
                }else if(firstChar != '+'){
                    return null;
                }

                if(len == 1) return null;

                ++i;
            }

            long result;
            int digit;
            for(result = 0L; i < end; result -= digit){
                digit = Character.digit(s.charAt(i++), radix);
                if(digit < 0){
                    return null;
                }

                result *= radix;
                if(result < limit + (long)digit){
                    return null;
                }
            }

            return negative ? result : -result;
        }
    }
}