二分查找框架

```java
/**
 * @author peng.wei
 * @version 1.0
 * @date 2021/3/21 14:25
 * @Description 二分查找算法框架
 */
public class BinarySearch {

/**
     * 二分查找算法
     * @param nums  原始数组
     * @param target    目标值
     * @return  目标值在原始数组中的位置
     */
    public static int binarySearch(int[] nums, int target) {
        int left = 0, right = nums.length - 1;
        while (left <= right) {
            int mid = left + (right - left) / 2;  // 为了防止 (left + right) 太大导致溢出
            if (nums[mid] < target) {left = mid + 1;}
            else if (nums[mid] > target) {right = mid - 1;}
            else if (nums[mid] == target) {return mid;}
        }
        return -1;
    }

/**
     * 寻找左侧边界的二分查找算法
     * @param nums  原始数组
     * @param target    目标值
     * @return  目标值在原始数组中的位置
     */
    public static Integer leftBond(int[] nums, int target) {
        int left = 0, right = arr.length - 1;
        int res = arr.length;  // 保存左侧边界
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (arr[mid] < target) {left = mid + 1;}
            else if (arr[mid] > target) {right = mid - 1;}
            else if (arr[mid] == target) {
                res = Math.min(res, mid);  // 更新左侧边界
                right = mid - 1;
            }
        }
        return res;
    }

/**
     * 寻找右侧边界的二分查找算法
     * @param nums  原始数组
     * @param target    目标值
     * @return  目标值在原始数组中的位置
     */
    public static Integer rightBond(int[] nums, int target) {
        int left = 0, right = arr.length - 1;
        int res = -1;  // 保存右侧边界
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (arr[mid] < target) {left = mid + 1;}
            else if (arr[mid] > target) {right = mid - 1;}
            else if (arr[mid] == target) {
                res = Math.max(res, mid);  // 更新右侧边界
                left = mid + 1;
            }
        }
        return res;
    }
}
  ```