--无序查找

     public static int Search(int[] a,int key){

         for(int i=0;i<a.length;i++){

             if(key==a[i]){

                 return i;

             }

         }

         return -1;

     }

 --折半查找

     public static int BinarySearch(int[] a,int key){

         int min,max,mid;

         min=0;

         max=a.length-1;

         mid =(min+max)/2;

         while(key!=a[mid]){

             if(key>a[mid]){

                 min=mid+1;

             }else{

                 max=mid-1;

             }

             if(max<min)

                 return -1;

             mid=(min+max)/2;

         }

         return mid;

     }

 --折半查找优化

     public static int BinarySearch_2(int[] a,int key){

         int min,max,mid;

         min=0;

         max=a.length-1;

         while(max>=min){

             mid =(min+max)>>1;

             if(key>a[mid]){

                 min=mid+1;

             }else if(key<a[mid]){

                 max=mid-1;

             }else{

                 return mid;

             }

         }

         return -1;

     }