#KOTLIN CODEPOINTS CODE#

JavaScript exposes Strings with 32-bit CodePoints, while Java and Native exposes 16-bit Chars using Surrogate Pairs for higher values.įor now, kotlinx-io only implements UTF_8, but allows to add custom charsets by extending the Charset class. Thus requiring linear time for seeking, slicing and getting length. Getting the length of a String represented as UTF-8 requires decoding the whole content, By being encoded by a variable length of bytes, The most widely used charset is UTF-8, which allows to represent most 7-bit ASCII characters as single byte,īut allows to represent the whole Unicode character set. Not all the charsets can represent the whole Unicode character set. Some charsets represent characters as single-byte, other represents characters with several fixed bytes per characters, encode ( 'HELLO', 1, 2, output ) Further details about Charsets Str.codePointCount(0, str.Val output : Output val charset = Charsets.

#KOTLIN CODEPOINTS CODE#

If you really need to, you can count the Code Points to get the number of characters, not the number of Code Units: String str = '𝕒𝕓𝕔' If we go back to our quiz, we can explain some of the anomalies: Java -> U+004A U+0061 U+0076 U+0061 // 4 Code Points Let that sink in: this means that the char type (as well as the Character class) in Java is not what we usually mean by a character. So if you have one supplementary character that consists of two Code Units, the length of that single character is two. The length is equal to the number of Unicode code units in the string. Let’s take a look at the Javadoc of the length() method of the String class it says the followings: Unicode Code Point: U+1D538 (see: /U+1D538)Īs you can see here A is encoded by one Code Unit while 𝔸 is encoded by two. a single at the end of the string, just ignore it.

The key thing here is that one or more Code Units may be required to encode a Code Point (character). PrimitiveIterator import import -58,6 +59,7. Supplementary characters ( Code Points) are encoded in two Code Units (see Wikipedia - UTF-16 for more information). The other planes contain the “supplementary” characters (from U+10000 to U+10FFFF).Ĭharacters ( Code Points) from the first plane are encoded in one 16-bit Code Unit with the same value. The first plane, the Basic Multilingual Plane (BMP) contains the “classic” characters (from U+0000 to U+FFFF). Unicode Code Points are logically divided into 17 planes (groups). Not the only way but that is what Java uses.

Code Unit is a bit sequence used to encode a character ( Code Point)Īs I mentioned above, UTF-16 is a way to encode Unicode characters.

Code Point is a unique integer value that identifies a character.

There are two important Unicode terms here, you need to know about: Code Point and Code Unit. That’s why the size of the Java char type is 2 bytes (2x8 = 16 bits). Unicode is a standard to represent text while UTF-16 is a way to encode Unicode characters. To understand the weirdness in Strings, you need to be familiar with some Encoding/Unicode terms.Īs you might know, Java uses UTF-16 to encode Unicode text. In the rest of the article, I’m going to explain why you might got unexpected results in the quiz and give you a few suggestions to avoid issues. What do you think, what is the length of the following Strings in Java?īy now, you might get why “Confusing Java Strings” is the title of this article. In order to demonstrate this, let me invite you for a little quiz: I also prepared a GitHub repo for you where you can find some code that you can use to try the examples out on your own: /jonatan-ivanov/java-strings-demo. In this article, I would like to show you a couple of confusing things in connection with Java Strings and give you a few suggestions to avoid issues with them.

Kotlin codepoints