How does a leading zero change a numeric literal in Java?

Question

My friends and I have puzzled over this statement in Java after seeing it and the answer. How does this work?

System.out.printf(\"%d\", 077);

Answer 1

When you define an literal integer number with a 0 prefix, the compiler will treat it as an integer base 8. (Octal).

Check at this post http://rodrigosasaki.com/2013/06/10/number-literals-in-java/

So, 77 value in Octal base is actually 63 in Decimal base.