Counting unique characters in a String given by the user

Question

I have to write a program that counts the uniques characters in a String given by the user. For example \"abc\" returns 3 and \"aabbccd\" returns 4. I am not allow to use advan

Answer 1

String myString = "";

for(int i=0; i< word.length(); i++) {
    if(myString.indexOf(word.charAt(i)) == -1) {
        System.out.println(word.charAt(i));
        myString = myString + word.charAt(i);
    }
}
return myString.length();

Answer 2

In case you are allowed to use Java Sets, The following code is readable, compact and doing the job smoothly

public static int countUniqueChar(String word){
    Set<Character> wordSet = new HashSet<>();
    for(Character c : word.toCharArray())
        wordSet.add(c);
    return wordSet.size();
}

Answer 3

Try to see if the following code helps you:

String myString = "";

for(int i=0; i< word.length(); i++) {

    if(myString.indexOf(word.charAt(i)) == -1) {
        System.out.println(word.charAt(i));
        myString = myString + word.charAt(i);
    }
}
return myString.length();

Answer 4

You can use HashSet collections for counting the unique elements in a string. It allow only unique element.

Code Snippet

public static int uniqueCount(String str) 
{
   HashSet<Character> al = new HashSet<Character>();
   char[] arr= str.toCharArray();
   for (int i=0; i<arr.length; i++) 
   {
      al.add(arr[i]);  
   }
   return al.size() ;
}  

Refer this link to get full code: ideone

Answer 5

public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    System.out.println("Please enter String:");
    int length = scanner.nextInt();
    char[] ch1 =  new char[length];
    String[] input = new String[length];
    for (int i = 0; i < length; i++) {
        String userInput = scanner.next();
        input[i] = userInput;
         ch1= userInput.toCharArray();

        Arrays.sort(ch1);
         System.out.println(ch1);
    }

Answer 6

It is extremely easy :)

public static int countUniqueCharacters(String input) {
    boolean[] isItThere = new boolean[Character.MAX_VALUE];
    for (int i = 0; i < input.length(); i++) {
        isItThere[input.charAt(i)] = true;
    }

    int count = 0;
    for (int i = 0; i < isItThere.length; i++) {
        if (isItThere[i] == true){
            count++;
        }
    }

    return count;
}

Example for input "aab"

First for-cycle goes 3 times, each time for one char.

Value of "a" is 97, so it turns isItThere[97] to true, then second "a" is involved, which is doing the same, isItThere[97] is set to true again (hence changing nothing).

After that "b" is involved, value of char "b" is 98, therefore isItThere[98] is set to true.

And then you have second for-cycle, where you cycle through the all isItThere array. If you find any true statement, you increment count. In our case, you find isItThere[97] and isItThere[98] as true statement, it means you increment twice and returning 2.