Convert unicode symbols to their codes

The Unicode standard starts with a sequence of characters that are sufficient for 16 bits (two bytes).

However, more and more scripts and symbols are added to it, and nowadays you can't represent all characters in 16 bits. The legal range of code points is from U+0 to U+10FFFF.

Unfortunately this doesn't work with Java char, which is only 16 bits and capable of representing values ​​from 0 to FFFF.

The most common western languages ​​have no problem with this - Latin ranges (including accents, Russian, Arabic, Hebrew, etc.) are all in the 16-bit range. Even common Chinese and Japanese characters are in this range.

However, most emoji are actually in the "extended" range, in the Unicode "Other Symbols and Pictographs" and "Emoticon" modules, from U+1F300 to U+1F5FF and U+1F600 to U+1F67F, respectively.

Characters in this range are represented as strings using the UTF-16 encoding, which basically uses two values char​​for each such character . So if a character's code point (its official unicode value) is in the range U+10000 to U+10FFFF , then two values, one in the range from U+D800 to U+DB7F ("high surrogate"), and one from The range of values ​​U+DC00 to U+DFFF ("low surrogate") is used to represent it.char

So when you read the value charAt(emoji_pos)in your program , you're actually only reading the first half of the actual character. In fact, all emojis in the "emoji" range have a high substitution characteristic of U+D83D.

So, to get the actual Unicode code point of the emoji, you need to convert the UTF-16 representation to the actual intvalue. A is charnot enough. You can then use the methods available in the Stringand Characterclass to do this .

charAtIn this case, you can use methods instead .codePointAt

So, instead of

char emoji_char = str.charAt(emoji_pos);

use:

int emojiCodePoint = str.codePoint(emojiPos);

For more information, read the UTF FAQ on the Unicode Consortium website .

Note: The Java coding convention is that variable, field names and method names should be in lower camel case: the first word starts with a lower case letter, the other words start with an upper case letter, and there are no underscores . So the variable name should emojiCodePointnot be emoji_code_point. Underscores are only acceptable in constant names (all uppercase, for example CASE_INSENSITIVE_ORDER) .