Why some of the Unicode character literals can't be used in Java source code?

Java provides escape sequences for several non-graphical characters. All characters can be specified as a hexidecimal Unicode character (\uxxxx) with some as an octal character (\ddd where the first d is limited to 0-3, and the others 0-7 - same as \u0000-\u00ff). There are certain special characters which can be represented by escape sequences:

The compiler translates Unicode characters at the first step of the compile cycle.

Using the Unicode escape characters '\u000a' for newline and '\u000d' for return in a String or comment produces a compile-error as they are interpreted, literally, as 'end-of-line'.

Instead, you should use the equivalent escape sequences: '\n' or '\r'.