递归二进制搜索Java

Question

I have an arraylist called sArray that holds a large list of correctly spelled words. I need to send a word to this recursive binary search method (key) and determine whether or not it is spelled correctly or not. I understand how a recursive binary search works however I am not sure how to determine whether or not I need to go left or right in searching sArray with my key word since I am dealing with Strings and not integers.

 public int bSearch(String key, int lowIndex, int highIndex) {

    if (lowIndex > highIndex) {
        System.out.print("The word is incorrect");
        return -1;
    }

    mid = (lowIndex + highIndex) / 2;
    if (sArray.get(mid).equals(key)) {
        return mid;
    } else if (key < sArray.get(mid)) {
        return bSearch(key, lowIndex, mid - 1);
    } else {
        return bSearch(key, mid + 1, highIndex);
    }
}

Answer 1

You can just as easily compare Strings as integers:

if (testString.compareTo(key) < 0) {
    ...
} else if (testString.compareTo(key) > 0) {
    ...
} else {
    ...
}

Answer 2

The compareTo method lets you compare any object that implements the Comparable interface. Since the String class implements the Comparable interface, compareTo will work in your method.

A handy trick to remember when using compareTo is thinking of it like subtraction:

a.compareTo(b) will return -1 if a - b results in a negative answer. (a comes before b when ordering them)

a.compareTo(b) will return 1 if a - b results in a positive answer. (a comes after b when ordering them)

a.compareTo(b) will return 0 if a - b results in 0. (a and b are identical when ordered)

So...

 if (key.compareTo(midValue) < 0) {

      //look to the left of mid
 }...