Why can't a long start with zero? [duplicate]

Answer 1

using leading zeroes for constants is indicating the octal notation, by which only digits 0..7 are allowed. so if you use leading zeroes for making number pretty print, that is a bad idea as the value it represents is different.

See http://docs.oracle.com/javase/specs/jls/se5.0/html/lexical.html#3.10.1 and watch out for "OctalNumeral".

Answer 2

When you put a 0 in front of an integer-type literal, it will interpret it as representing an octal number. Since "9" isn't a valid digit for octal numbers, that might be what's going on. Try printing out the (decimal) value of "010L" and see whether is says "8" to confirm.

Note: not sure if Java does this, or if this is purely an artifact of Eclipse. If the latter, printing out 010L would show 10. If the former, you'd see 8. If it's just an artifact of Eclipse, you can confirm by trying 01L, 02L, ..., 07L, which should all work, and 08L and 09L which would fail.