why is not (123 == 0123) in java?

Question

I am developing an application in Android using Eclipse. I wrote the following code and in tests the first and third \"if\" block is not reachable. Why?

Answer 1

because 0123 in not decimal digit its octal (base 8) so this is equal to 83

To convert a number k to decimal, use the formula that defines its base-8 representation:

0123 base-8 = 83 decimal

0123 = (3*8^0) +(2*8^1)+(1*8^2)+(0*8^4)
     =3+16+64+0
     =83   

An octal numeral consists of an ASCII digit 0 followed by one or more of the ASCII digits 0 through 7 and can represent a positive, zero, or negative integer.

Note: Octal values are denoted in java by leading zero normal decimal number cannot have a leading zero