202407191538
Status: #idea
Tags: Java

char

• Each code point is a Unicode scalar value. Supplementary characters are those which cannot be encoded in 16-bits (U+10000 to U+1FFFF)

• Java uses UTF-16 to encode its characters.
• Supplementary characters are encoded using 2 characters

Unicode encodings

• A character is referred to as a unicode code point
• Unicode has 3 encodings
  • UTF-32 → Fixed length encoding of 32 bits
  • UTF-16 → Variable length encoding in 16/32 bits
  • UTF-8 → Variable length encoding in 8/16/24/32 bits

UTF-8

• Notice that 1 byte code points start with $0$
• 2, 3, 4 byte code points start with 2, 3, 4 $1^{\prime }s$ respectively. The trailing bytes all start with $10$

References

1. https://www.oracle.com/technical-resources/articles/javase/supplementary.html
2. https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/lang/Character.html#unicode
3. https://www.wikiwand.com/en/UTF-8#Encoding