medium_21_2.java

public static int firstOccurrence (int values[], int target) {
	int left = 0;
	int mid = 0;
	int right = values.length - 1;
	int pos = -1;
	
	while (left <= right) {
		mid = (left + right) / 2;

		if (target == values[mid]) {
			pos = mid;
			right = mid - 1;
		} else if(target > values[mid]) {
			left = mid + 1;
		} else {
			right = mid - 1;
		}
	}
	return pos;
}