01 — char and String

Java's text model was designed in 1995, when Unicode fit in 16 bits and a char could hold any character. Unicode outgrew that in 1996. Java could not change char without breaking every program ever written, so it did the only compatible thing: it kept char at 16 bits and let a single character occupy two of them.

Everything in this chapter follows from that one decision. It is not a bug, and it is not going to be fixed. It is a thirty-year-old compatibility promise that you have to know about, because the method named length() does not return the length.

Lesson	The one thing
A char is not a character	16 bits stopped being enough in 1996
Length is three different numbers	storage, characters, or what a reader sees — pick
Reverse and substring cut characters in half	the standard library will let you, without an error