Messed up with Java Declaration

Messed up with Java Declaration

why java constant have strange behaviour (Unicode Character and normal
representation).. I mean see below example. Note : All code is in java
language.
char a = '\u0061'; //This is correct
char 'a' = 'a'; //This gives compile time error
char \u0061 = 'a'; //this is correct no error
ch\u0061r a = 'a'; //This too works
ch'a'r a = 'a'; // This really is confusing compile time error
Why last declaration is not works whereas ch\u0061r a='a'; works?