二分查找 java代码

import java.util.Optional;


public class MyArray {
    public static void main(String[]args) {
        int[] arr = new int[]{1,2,3};
        for (int i = 0; i < arr.length; i++) {
            System.out.println("arr[" + i + "]=" + arr[i]);
        }
        Optional<Integer> num = searchByHalf(arr, 2);
        if (num.isPresent()) {
            System.out.println(num.get());
        } else {
            System.out.println("not find");
        }

    }

    public static Optional<Integer> searchByHalf(int[] arr, int target) {
        int low = 1;
        int high = arr.length;
        while (low <= high) {
            int middle = (low+high)/2;
            if (arr[middle - 1] == target) { 
                return Optional.of(middle);
            } else if (arr[middle - 1] < target) {
                low = middle+1;
            } else if (arr[middle - 1] > target) {
                high = middle-1;
            }
        }
        return Optional.ofNullable(null);
    }
}