Showing error when initializing with 0 at its beginning.can't understand the reason behind it,can anyone tell me

Question

    int a=019;
    int b;
    b=a;
    System.out.println(a);

Main.java:13: error: integer number too large: 019
int a=019;
^
1 error

Answer 1

Integer literals beginning with a "0" are treated as octal. The permissible digits are 0 through 7.

Hexadecimal literals begin with 0x, e.g. 0xA