java二分法查找演示

public class DemoHalfFind {

 public static void main(String[] args) {
  // TODO Auto-generated method stub
  double arr[]={1,2,3,4,5,10,100,101};
  double target=100;
  int targetindex=HalfFind.find(arr,0,arr.length-1,target);
  if (targetindex==-1)
  {
   System.out.println("找不到"+target);
  }
  else
  {
   System.out.println("找到目标，下标为"+targetindex);
  }
 }

}

class HalfFind//二分法查找类
{
 public static int find(double arr[],int beginindex,int endindex,double target)//查找方法
 {
  int middleindex=(beginindex+endindex)/2;
  double middlevalue=arr[middleindex];
  int targetindex=-1;
  if (beginindex<=endindex)//递归条件
  {
   if (middlevalue>target)
   {
    targetindex=find(arr,beginindex,middleindex-1,target);
   }
   else if (middlevalue==target)
   {
    return middleindex;
   }
   else
   {
    targetindex=find(arr,middleindex+1,endindex,target);
   }
  }
  return targetindex;
 }
}