Java assignment static variable

When I assign the value of a static int to another int, it performs the assignment in an order that does not seem to follow the Java operation order Shouldn't it be done before =?

public class Book
{
  private int id;
  private static int lastID = 0;

  public Book ()
  {
    id=lastID++;
  }
}

In the first book I built, the ID was 0 It should not be 1, because should lastid happen first?

Solution

– > Yes, first evaluate the following:

Your expression:

id = lastID++;

Equivalent to the following expression

temp = lastId;    // temp is 0
lastID = lastID + 1;  // increament,lastId becomes 1
id = temp;   // assign old value i.e. 0

So your ID is 0. In this case, you should use pre increase operator():

public class Book
{
  private int id;
  private static int lastID = 0;

  public Book ()
  {
    id = ++lastID; // pre-increament
  }
}