折半查找

一.while条件:while(low <= high).最简单的可以向,如果最后剩下一个元素进行比较,如果条件为low < high,则不会进入比较,从而得不到结果
二.对于Comparable这个类中,对两个元素进行比较,使用val1.compareTo(val2)方法(当然气候要对compareTo方法进行重写),val1==val2,return 0;val1 <　val2,return -　　    　　  1;val1　>　val2,return 1;
三.注意low = center + 1和high = center - 1;

public class BinarySeacher {
    public static final int NOT_FOUND = -1;
    public static <AnyType extends Comparable<? super AnyType>> int binarySeacher(AnyType [] a, AnyType x){
        int low = 0,high = a.length - 1;

        while(low <= high ){
            int center = ( low + high ) / 2;
            if(a[center].compareTo(x) < 0)
                low = center + 1;
            else if(a[center].compareTo(x) > 0)
                high = center - 1;
            else
                return center;
        }

        return NOT_FOUND;
    }
}