3.10.6 Escape Sequences for Characters and String Literals
 
where it talks about OctalEscape:
          
    \ZeroToThree OctalDigit OctalDigit
 
javac gives a compilation error on "\477".
 
The string "\477" is questionable, but the grammar
explicitly allows for:
 
        \OctalDigit OctalDigit
 
so the \47 fits this rule, and the following 7 is just another character
in the string.
 
There is nothing in the JLS that says that "\477" is an error, and the grammar
allows for it. This could alternately be considered a bug in
javac when it reports an error on "\477".