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?

When I add a leading zero to a number, the equal operator returns false.

int var = 123; if (var == 0123) {     //not reachable } if (var == 123) {     //reachable } if (var == (int)0123) {     //not reachable } if (var == (int)123) {     //reachable } 

Answer 1

0123 is an octal number (leading 0), while 123 is a decimal number.

so 0123 actually equals to 83.

Answer 2

Any integer Number Leading With Zero is octal Number (base 8).

0123 is octal Number and 123 is Decimal Number

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