java - Int with leading zeroes - unexpected result

Question

Given the following sample:

public class Main {
    public static void main(String[] args) {
        System.out.println(1234);
        System.out.println(01234);
    }
}

The Output is:

1234
668

Why?

Answer 1

This is because integer literals with a leading zero are octal integers (base 8):

1 * 8^3 + 2 * 8^2 + 3 * 8 + 4 = 668