Binary search

class BinarySearch {

List data

// You may assume for this exercise that the input data is sorted in ascending order.
BinarySearch(List data) {
    this.data = data
}

 List<Integer> getSlice(int start, int end){

    start = Math.max(0,start);
    end = Math.min(this.data.size(), end);
    return this.data.subList(start, end);
}

int indexOf(item) {
    int halfLength;
    int index = this.data.indexOf(item);
    if(this.data.size() % 2 ==0){
        halfLength = this.data.size()/2;
        while(this.data.size()>0){
            if(this.data.get(halfLength-1)==item) return index;
            else if (this.data.get(halfLength-1) > item){
                    this.data = getSlice(0, halfLength-1);
                }
             else if (!this.data.get(halfLength-1).equals(item)){
                    this.data = getSlice(halfLength-1, this.data.size()); 
                if(this.data.get(halfLength-1).equals(item)) {
                    
                    index += (halfLength-1);
                    return index;
                }
                else indexOf(item);}
        }
    }
    else {
            halfLength= this.data.size()/2+1;
            if(this.data.get(halfLength-1) == item) return index;
             else if (this.data.get(halfLength-1) > item){
                this.data = getSlice(0, halfLength-1);
                }
             else if (this.data.get(halfLength-1) < item){
                this.data = getSlice(halfLength-1, this.data.size());
                }
        }
    return index;
}

}