Changing a string to a Char array

Question

Once a value is stored as a String, how can you loop through string and assign each value to a char array? The occurrences of every vowel in array must also be counted.

This is my current code:

public class Part1_5 {

  /**
   * Method that gets user name and stores it as a string. Each value then
   * assign to a char array. no of vowels are counted and no of each printed
   */
  public static void main(String[] args) {

    // Setting up scanner
    Scanner scanner = new Scanner(System.in);

    // declaring string for name
    String userName = null;

    // declaring ints to hold total no of each vowel
    int totalOfA = 0;
    int totalOfE = 0;
    int totalofI = 0;
    int totalofO = 0;
    int totalofU = 0;

    // Get user input for name
    System.out.println("Please enter your Name...");
    userName = scanner.nextLine();

    for (int loop = 0; loop < userName.length(); loop++) {

      // declaring char array
      char[] letter = userName.toCharArray();

      if (userName.charAt(0) == 'a') {

        totalOfA++;

      }

    }

    System.out.println(totalOfA);

  }

}

Answer 1

String str = "stackoveflow";
char[] aa= str.toCharArray();

And to directly get a char from string, you can use:

str.charAt(i);

Answer 2

What about iterating over (and counting) all characters in a String?

Does the count of the vowels have to be case sensitive?

Map<Character, Integer> count = new HashMap<Character, Integer>();
char[] chars = "this is a test".toCharArray();
for (char curr : chars){
    Integer tmp = count.get(curr);
    if (tmp == null){ tmp = new Integer(0); }
    tmp++;
    count.put(curr, tmp);    
}
System.out.println(count.get("a".charAt(0)));
System.out.println(count.get("e".charAt(0)));
System.out.println(count.get("i".charAt(0)));
System.out.println(count.get("o".charAt(0)));
System.out.println(count.get("u".charAt(0)));

Which gives you...

1
1
2
null
null

Handling null is trivial - e.g. result == null ? 0 : result

Edit: Improved with 100% more case insensitivity!!

Map<Character, Integer> count = new HashMap<Character, Integer>();
for (char curr :  "this IS a test".toLowerCase().toCharArray()){
    Integer tmp = count.get(curr);
    count.put(curr, tmp == null ? 1 : ++tmp);
}

And the same thing, but in Groovy...

def count = "this IS a test".toLowerCase().collect().countBy{it}

Answer 3

Use the counting variable in the for loop to specify the position in the userName String to count up the vowels.

Also, you don't even need a char array for the method that you're doing. But if you did need one, you should define it before you start the for loop. Why create it so many times?

You asked how to loop through the String and assign each value to a char array, but you don't need to do that: you can simply do what you did, char[] letter = userName.toCharArray();.

public class Part1_5 {
    public static void main(String[] args) {

        // Setting up scanner
        Scanner scanner = new Scanner(System.in);

        // declaring string for name
        String userName = null;

        // declaring ints to hold total no of each vowel
        int totalOfA = 0,totalOfE = 0,totalofI = 0,totalofO = 0,totalofU = 0;

        // Get user input for name
        System.out.println("Please enter your Name...");
        userName = scanner.nextLine();

        // declaring char array (declare it once, before the loop)
        char[] letter = userName.toCharArray();

        for (int loop = 0; loop < userName.length(); loop++) {

            // check and count for any vowel at every iteration of the loop
            if (userName.charAt(loop) == 'a')
                totalOfA++;
            else if (userName.charAt(loop) == 'e')
                totalOfE++;
            else if (userName.charAt(loop) == 'i')
                totalOfI++;
            else if (userName.charAt(loop) == 'o')
                totalOfO++;
            else if (userName.charAt(loop) == 'u')
                totalOfU++;
        }
        System.out.println(totalOfA);
    }
}

Answer 4

if (userName.charAt(loop) == 'a') {