How to detect in Java if string contains Cyrillic?

Try the following:

Pattern.matches(".*\\p{InCyrillic}.*", text)

You may also avoid a regex and use the class Character.UnicodeBlock:

for(int i = 0; i < text.length(); i++) {
    if(Character.UnicodeBlock.of(text.charAt(i)).equals(Character.UnicodeBlock.CYRILLIC)) {
        // contains Cyrillic
    }
}

Here is another way to do the same with streams in java 8:

text.chars()
        .mapToObj(Character.UnicodeBlock::of)
        .filter(Character.UnicodeBlock.CYRILLIC::equals)
        .findAny()
        .ifPresent(character -> ));

Or another way, keeping the index:

char[] textChars = text.toCharArray();
IntStream.range(0, textChars.length)
                 .filter(index -> Character.UnicodeBlock.of(textChars[index])
                                .equals(Character.UnicodeBlock.CYRILLIC))
                 .findAny() // can use findFirst()
                 .ifPresent(index -> );

Please note: I'm using char array here rather than String due to performance advantage of getting an element by index.