java数组中根据元素查找位置 索引

               

Arrays提供了一个方便查询的方法 ：Arrays.binarySearch（）；

    public static void main(String[] args) {        // TODO Auto-generated method stub        String[] arrays = new String[]{"a","b","c","d","e","fff","g","h","i","j",};        int positon = Arrays.binarySearch(arrays, "fff");           System.out.println("position is:"+positon);    }

测试结果：

    position is:5  

这个方法也是用的二分法实现的：

    public static int binarySearch(char[] array, int startIndex, int endIndex, char value) {              checkBinarySearchBounds(startIndex, endIndex, array.length);                  int lo = startIndex;              int hi = endIndex - 1;                    while (lo <= hi) {                  int mid = (lo + hi) >>> 1;//无符号右移                  char midVal = array[mid];                        if (midVal < value) {                      lo = mid + 1;                  } else if (midVal > value) {                      hi = mid - 1;                  } else {                      return mid;  // value found                  }              }              return ~lo;  // value not present          }

转载：http://blog.csdn.net/mattdong0106/article/details/22676807