Why does this cause an infinite loop

Question

Consider this simple code:

 // E1 
  public void doTest(String pattern) {
    int counter = 0;

    while (counter < 3) {
        counter = counter++;
    }
    System.out.println("Done");
}

This causes an infinite loop.

However if the statement that increments the counter is written like this:

E2.  counter = ++counter;

or this

E3.    counter++;

It terminates normally. I understand that the incrementing occurs after the assignment in the version that fails which explains why E2 works, but I thought java assigned the results of an increment in the variable that is incremented as in E3. So I'm perplexed as to why E1 fails but E3 does not.

Answer 1

counter = counter++;

The above code has no effect on counter. It is effectively same as:

int temp = counter;
counter++;
counter = temp;

So, the value of counter is not changing at all.

On the other hand, if you use:

counter = ++counter;

The counter is incremented first, and then is re-assigned to counter. Essentially, you can simply ignore the assignment part, and keep it simply this:

counter++; // Or ++counter