public class Paixu {    public static void main(String[] args) {        int[]arr={1,2,8,10,18,22,28,100,20};/*        //选择排序  从小到大        for (int i = 0; i < arr.length-1; i++) {            for (int j = i+1; j < arr.length; j++) {                if (arr[i]>arr[j]) {                    int tmp=arr[i];                    arr[i]=arr[j];                    arr[j]=tmp;                }            }        }*/                //冒泡排序 从小到大    for (int i = 0; i < arr.length; i++) {        for (int j = 0; j < arr.length-i-1; j++) {            if (arr[j]>arr[j+1]) {                int tmp=arr[j];                arr[j]=arr[j+1];                arr[j+1]=tmp;                            }        }    }                System.out.println(Arrays.toString(arr));        //二分法                System.out.println(search(arr, 20));    }    public static int search(int[]arr,int key){        int start=0;        int end=arr.length-1;        while(arr[start]<=arr[end]){            int middle=(end+start)/2;            if (key
     
      arr[middle]){                start=middle+1;            }else{                return middle;            }        }        return -1;            }}