Java firstPosition算法

int firstPosition(int x, int [] a) {

    int lower = 0;
    int upper = a.length;

    while (lower != upper) {
    int mid = (lower + upper) / 2;

    **if (x <= a[mid]) {** // the line I don\'t understand
    upper = mid;
    } else {
    lower = mid + 1;
    }
    return (lower);
}

while ( 3 ! = 0 ) { // execute line

int mid = lower + upper / 2 - which is (0 + 10)/2 = 5

if ( x <= a[mid]) // I assume that means if 3 is less than or equal to 5? 5 then replace mid with 5 and then...

lower = mid + 1 // 5+1 = 6, return 6 as lower?

x

+---+---+---+---+---+----+
| 1 | 3 | 5 | 7 | 9 | 11 |
+---+---+---+---+---+----+
  ^                        ^
  |                        |
lower                    upper

9

5

9

5

9

if

else

+---+---+---+---+---+----+
| 1 | 3 | 5 | 7 | 9 | 11 |
+---+---+---+---+---+----+
              ^            ^
              |            |
            lower        upper