Incomprehensible display of the results of several successive in(de)crementations?

Question

Java

class  temp{
  public static void main(String args[]){
    int t = 011;
    System.out.println(t);    //9
    System.out.println(t++);  //выводится на экран 9, почему не 10?
    System.out.println(t++);  //10
    System.out.println(t++);  //11
  }
}

The output I expected was:

9
10
11
12

and got:

9
9
10
11

Please explain why I have what I have?
PS: taking this opportunity, question number two: how to display numbers not in decimal form, but in octal form, so that the output would start with the octal number 12, or does incrementation in this example mean: first transfer to decimal and then ++?

Answer 1

A post-increment (i++) differs from a pre-increment in that it returns the value it had before the increment, changing the value of the variable itself. This is clearly seen in the C++ example . The semantics in the languages ​​is the same.
To convert to octal, you can use the Integer.toOctalString(int) method;

Answer 2

try writing System.out.println(++t);

Answer 3

There is already a correct answer, so I'll just give advice :).
Avoid using unary operators in expressions and function calls. Compilers are good at optimizing