问Java中的数组列表二分查找

EN

public void contains(String key) {
    System.out.println("Initializing");
    if(isSorted()) {
        int first = 0;
        int last = this.size() - 1;
        while(last >= first) {
            int mid = (first + last) / 2;
            if (this.get(mid).equals(key)) {
                System.out.println(this.get(mid));
            }
            if (this.get(mid).compareTo(key) == 1) {
                System.out.println(this.get(mid));
                first = mid + 1;
            }
            if (this.get(mid).compareTo(key) == -1) {
                System.out.println(this.get(mid));
                last = mid - 1;
            }
        }
    }
    else {
        System.out.println("Character does not exist");
    }
}