codepoint : Java Glossary

Unicode was extended to 32 bits, with the corresponding UTF-16 encoding also extended with a clumsy system of surrogate characters to encode the 32-bit characters above 0xffff.

The term codepoint in Java tends to be used to mean a slot in the 32-bit Unicode assignment, though I suspect the term is also valid to mean a spot in Unicode-16 or any other character set.

Java now straddles the 16-bit and 32-bit worlds. You might think Java would now have a 32-bit analog to Character, perhaps called CodePoint, and a 32-bit analog to String, perhaps called CodePoints, but it does not. Instead, Strings and char[] are permitted to contain surrogate pairs which encode a single high-32-bit codepoint.

StringBuilder.appendCodePoint( int codepoint ) will accept 32-bit codepoints to append.

StringBuilder.append( int number ) just converts the number to a String and adds that, not what you want!

FontMetrics.charWidth( int codepoint ) will tell you the width in pixels to render a given codepoint.

Character.isValidCodePoint( int codepoint ) will tell you if there is a glyph assigned to that codepoint. That is still no guarantee your Font will render it though. Character. codePointAt and codePointBefore let you deal with 32-bit codepoints encoded as surrogate pairs in char arrays. Most of the Character methods now have a version that accepts an int codepoint such as toLowerCase.

Iterating Over A String