RadomValueFromArrayBasedOnWeightAge

RadomValueFromArrayBasedOnWeightAge

  //smallest element greater than or equal to key
    public static <T extends Comparable<T>> int findCeil(final T[] array, final T key){
        int low=0;
        int high = array.length-1;
        while (low<high){
            int mid = low + (high-low)/2;
            if(key.compareTo(array[mid])>0){
                low = mid+1;
            }else{
                high = mid;
            }
        }
        if(array[low].compareTo(key)>=0){
            return low;
        }else{
            return -1;
        }
    }

 public static <T> T getRandomObjectWithGivenProbability(T[] array, Integer[] frequency){
        Integer[] prefix = new Integer[frequency.length];
        prefix[0] = frequency[0];
        for(int i=1;i<prefix.length;i++){
            prefix[i]=prefix[i-1]+frequency[i];
        }

        Random r = new Random();
        Integer rand = r.nextInt(prefix[prefix.length-1])+1;
        int index = findCeil(prefix,rand);
        return array[index];
    }