Question: I have an assignment where I have perform letter frequency analysis by iterating over the characters within a string. 

I am unsure how to use an array to store the frequency of each letter. The array must be in alphabetical order and also store non-alphabetical characters (including spaces)

Unfortunately I have to use an array to store the frequency.

What would be the best way to complete this task in Java?

Answer: 
Much efficient way using streams

```
Map<Character, Long> freq = Arrays.stream(arr).
                collect(Collectors.groupingBy(Character::charValue, Collectors.counting()));

```
Ont direct way is to use 2 arrays, one for storing the character which appears in the string with case sensitive and the other one for storing its corresponding frequency. 

Both arrays are declared with the size of the length of string, following sample code shows how to achieve what you want by using just array and simple logic.

**Sample code**

```
String str = "The array must be in alphabetical order and also store non-alphabetical characters (including spaces)";

char[] charArr = new char[str.length()];
int[] freqArr = new int[str.length()];
int idx = 0;
for (int i = 0; i < str.length(); i++) {
    char c = str.charAt(i);
    boolean isFound = false;
    for (idx = 0; idx < str.length(); idx++) {
        if (freqArr[idx] == 0) {
            break;
        }
        if (c == charArr[idx]) {
            freqArr[idx]++;
            isFound = true;
            break;
        }
    }
    if (!isFound) {
        charArr[idx] = c;
        freqArr[idx]++;
    }
}

//Sort charArr and freqArr arrays
char tempChar;
int tempFreq;
for (int i = 1; i < str.length(); i++) {
    for (int j = i; j > 0; j--) {
        if (charArr[j] < charArr [j - 1]) {
            tempChar = charArr[j];
            charArr[j] = charArr[j - 1];
            charArr[j - 1] = tempChar;

            tempFreq = freqArr[j];
            freqArr[j] = freqArr[j - 1];
            freqArr[j - 1] = tempFreq;
         }
    }
}

```

**Print the letter frequency**

```
for (int i = 0; i < str.length(); i++) {
    if (freqArr[i] != 0) {
        System.out.printf("%s:%d", charArr[i], freqArr[i]);
        System.out.println();
    }
}

```

**Console output**

> 
> [ :13],[(:1],[):1],[-:1],[T:1],[a:13],[b:3],[c:6],[d:3],[e:8],...
> 
> 
>