Easiest way of checking if a string consists of unique characters?

Question

I need to check in Java if a word consists of unique letters (case insensitive). As straight solution is boring, I came up with:

1. For every char in a string che

Answer 1

Here's the code I wrote for Kache's answer(referred from cracking the code and modified):

public boolean check() {
    int[] checker = new int[8];
    String inp = "!a~AbBC#~";
    boolean flag = true;
    if (inp.length() > 256)
        flag = false;
    else {
        for(int i=0;i 0) { 
                flag = false;
                break;
            }
            else
                checker[index] = checker[index] | 1<