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I've got a 6 char long string, and I would like to check, if there is just one from each character. How to?

jaraipali
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    Please give example input and code you are trying – OneCricketeer May 20 '17 at 19:03
  • More expansive explanation for working with strings you can have here: http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java and https://www.tutorialspoint.com/java/java_strings.htm and https://docs.oracle.com/javase/tutorial/java/data/manipstrings.html – Vasyl Lyashkevych May 20 '17 at 19:20

2 Answers2

3

You could compare the number of distinct characters to the length of the string:

boolean charMoreThanOnce = s.chars().distinct().count() < s.length();
Mureinik
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    As much as I like such nice, clean, precise answers; I still feel tempted to not upvote; as this very much looks like you just did somebody's homework. Not that he will be able to make much out of this, but still. – GhostCat May 20 '17 at 19:08
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    Is it splitting hairs to point out that [it doesn't work for `""`](http://ideone.com/dyN8ym)? – Andy Turner May 20 '17 at 19:11
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You can do it using a Set. You need unique elements and Set gurantees you containing the unique elements. HashSet is implementation of Set, you can use it to implement this idea. 

public boolean ifAllCharsUnique(String input){
    char[] arr = input.toCharArray();
    int length = arr.length;
    Set<Character> checker = new HashSet<>();
    for(int i =0 ; i < length; i++){
         if(checker.contains(arr[i]){
               return false;
         }
         checker.add(arr[i]);
    }
    return true;
}
nits.kk
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  • With this method, I create a new array (or ArrayList ? ) < checker > , which only contains unique characters? – jaraipali May 20 '17 at 19:51