Better way to generate array of all letters in the alphabet

char[] alphabet = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};

This getAlphabet method uses a similar technique as the one described this the question to generate alphabets for arbitrary languages.

Define any languages an enum, and call getAlphabet.

char[] armenianAlphabet = getAlphabet(LocaleLanguage.ARMENIAN);
char[] russianAlphabet = getAlphabet(LocaleLanguage.RUSSIAN);

// get uppercase alphabet 
char[] currentAlphabet = getAlphabet(true);
    
System.out.println(armenianAlphabet);
System.out.println(russianAlphabet);
System.out.println(currentAlphabet);

Result

I/System.out: աբգդեզէըթժիլխծկհձղճմյնշոչպջռսվտրցւփքօֆ

I/System.out: абвгдежзийклмнопрстуфхцчшщъыьэюя

I/System.out: ABCDEFGHIJKLMNOPQRSTUVWXYZ

private char[] getAlphabet() {
    return getAlphabet(false);
}

private char[] getAlphabet(boolean flagToUpperCase) {
    Locale locale = getResources().getConfiguration().locale;
    LocaleLanguage language = LocaleLanguage.getLocalLanguage(locale);
    return getAlphabet(language, flagToUpperCase);
}

private char[] getAlphabet(LocaleLanguage localeLanguage, boolean flagToUpperCase) {
    if (localeLanguage == null)
        localeLanguage = LocaleLanguage.ENGLISH;

    char firstLetter = localeLanguage.getFirstLetter();
    char lastLetter = localeLanguage.getLastLetter();
    int alphabetSize = lastLetter - firstLetter + 1;

    char[] alphabet = new char[alphabetSize];

    for (int index = 0; index < alphabetSize; index++) {
        alphabet[index] = (char) (index + firstLetter);
    }

    if (flagToUpperCase) {
        alphabet = new String(alphabet).toUpperCase().toCharArray();
    }

    return alphabet;
}

private enum LocaleLanguage {
    ARMENIAN(new Locale("hy"), 'ա', 'ֆ'),
    RUSSIAN(new Locale("ru"), 'а','я'),
    ENGLISH(new Locale("en"), 'a','z');

    private final Locale mLocale;
    private final char mFirstLetter;
    private final char mLastLetter;

    LocaleLanguage(Locale locale, char firstLetter, char lastLetter) {
        this.mLocale = locale;
        this.mFirstLetter = firstLetter;
        this.mLastLetter = lastLetter;
    }

    public Locale getLocale() {
        return mLocale;
    }

    public char getFirstLetter() {
        return mFirstLetter;
    }

    public char getLastLetter() {
        return mLastLetter;
    }

    public String getDisplayLanguage() {
        return getLocale().getDisplayLanguage();
    }

    public String getDisplayLanguage(LocaleLanguage locale) {
        return getLocale().getDisplayLanguage(locale.getLocale());
    }

    @Nullable
    public static LocaleLanguage getLocalLanguage(Locale locale) {
        if (locale == null)
            return LocaleLanguage.ENGLISH;

        for (LocaleLanguage localeLanguage : LocaleLanguage.values()) {
            if (localeLanguage.getLocale().getLanguage().equals(locale.getLanguage()))
                return localeLanguage;
        }

        return null;
    }
}

I think that this ends up a little cleaner, you don't have to deal with the subtraction and indexing:

char[] alphabet = "abcdefghijklmnopqrstuvwxyz".toCharArray();