Task: Determine if a string has all unique characters
Java: import java.util.HashMap;
import java.util.Map;



public class StringUniqueCharacters {

    public static void main(String[] args) {
        System.out.printf("%-40s  %2s  %10s  %8s  %s  %s%n", "String", "Length", "All Unique", "1st Diff", "Hex", "Positions");
        System.out.printf("%-40s  %2s  %10s  %8s  %s  %s%n", "------------------------", "------", "----------", "--------", "---", "---------");
        for ( String s : new String[] {"", ".", "abcABC", "XYZ ZYX", "1234567890ABCDEFGHIJKLMN0PQRSTUVWXYZ"} ) {
            processString(s);
        }
    }
    
    
    
    private static void processString(String input) {
        Map<Character,Integer> charMap = new HashMap<>(); 
        char dup = 0;
        int index = 0;
        int pos1 = -1;
        int pos2 = -1;
        for ( char key : input.toCharArray() ) {
            index++;
            if ( charMap.containsKey(key) ) {
                dup = key;
                pos1 = charMap.get(key);
                pos2 = index;
                break;
            }
            charMap.put(key, index);
        }
        String unique = dup == 0 ? "yes" : "no";
        String diff = dup == 0 ? "" : "'" + dup + "'";
        String hex = dup == 0 ? "" : Integer.toHexString(dup).toUpperCase();
        String position = dup == 0 ? "" : pos1 + " " + pos2;
        System.out.printf("%-40s  %-6d  %-10s  %-8s  %-3s  %-5s%n", input, input.length(), unique, diff, hex, position);
    }

}

Python: 

from itertools import groupby



def duplicatedCharIndices(s):
    
    def go(xs):
        if 1 < len(xs):
            duplicates = list(filter(lambda kv: 1 < len(kv[1]), [
                (k, list(v)) for k, v in groupby(
                    sorted(xs, key=swap),
                    key=snd
                )
            ]))
            return Just(second(fmap(fst))(
                sorted(
                    duplicates,
                    key=lambda kv: kv[1][0]
                )[0]
            )) if duplicates else Nothing()
        else:
            return Nothing()
    return go(list(enumerate(s)))




def main():
    

    def showSample(s):
        return repr(s) + ' (' + str(len(s)) + ')'

    def showDuplicate(cix):
        c, ix = cix
        return repr(c) + (
            ' (' + hex(ord(c)) + ') at ' + repr(ix)
        )

    print(
        fTable('First duplicated character, if any:')(
            showSample
        )(maybe('None')(showDuplicate))(duplicatedCharIndices)([
            '', '.', 'abcABC', 'XYZ ZYX',
            '1234567890ABCDEFGHIJKLMN0PQRSTUVWXYZ'
        ])
    )






def fTable(s):
    
    def go(xShow, fxShow, f, xs):
        ys = [xShow(x) for x in xs]
        w = max(map(len, ys))
        return s + '\n' + '\n'.join(map(
            lambda x, y: y.rjust(w, ' ') + ' -> ' + fxShow(f(x)),
            xs, ys
        ))
    return lambda xShow: lambda fxShow: lambda f: lambda xs: go(
        xShow, fxShow, f, xs
    )





def Just(x):
    
    return {'type': 'Maybe', 'Nothing': False, 'Just': x}



def Nothing():
    
    return {'type': 'Maybe', 'Nothing': True}



def fmap(f):
    
    return lambda xs: [f(x) for x in xs]



def fst(tpl):
    
    return tpl[0]



def head(xs):
    
    return xs[0] if isinstance(xs, list) else next(xs)



def maybe(v):
    
    return lambda f: lambda m: v if (
        None is m or m.get('Nothing')
    ) else f(m.get('Just'))



def second(f):
    
    return lambda xy: (xy[0], f(xy[1]))



def snd(tpl):
    
    return tpl[1]



def swap(tpl):
    
    return (tpl[1], tpl[0])



if __name__ == '__main__':
    main()