数组(二分查找)

importjava.util.Arrays;//导入数组包       二分查询

publicclass Lx

{

       public static void main(String[] args)

       {

              //创建数组

              int[] arr={2,6,3,11,23};

              //从小到大排序,调用方法

              Arrays.sort(arr);

              //打印输出排序后的数组

              System.out.println(Arrays.toString(arr));

              //先定义第一个数,中间的数,最后个数的初始值.

              int start=0;

              int middle=0;

              int end=arr.length-1;

              //给想要找的数进行赋值

              int key=2;

              //while循环

              while(true)

              {

                     middle=(start+end)/2;

                     //判断当中间位置的那个数刚刚为key这个数,则查询成功

                     if(arr[middle]==key)

                     {

                            System.out.println("你要找的值在"+middle+"下标");

                            break;

                     }

                     //当中间位置这个数大于key,则将middle-1赋值给end继续查找

                     if(arr[middle]>key)

                     {

                            end=middle-1;

                           

                     }

                     //当中间位置这个数小于key,则将middle+1赋值给start继续查找

                     if(arr[middle]<key)

                     {

                            start=middle+1;

                           

                     }

                     //不存在start>end这种情况,无法查询

                     if(start>end)

                     {

                            System.out.println("查询结果不存在");

                            break;

                     }

              }

             

       }

}