Clarification about “int” number that begins with 0

Question

public class Test {

    public static void main(String[] args) {
        int i = 012;
        System.out.println(i);
    }
}

Why the output is : <

Answer 1

See the JLS:

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

It's a good practice to write:

int i = 0_12;

It might be clearer now, i in decimal is 2*8⁰ + 1*8¹ = 10.