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import java.util.Arrays;public class Test {	int test[] = {49,38,65,97,76,13,27,49,78,34,12,64,5,4,62,99,98,54,101,56,17,18,23,34,15,35,25,53,51,111,222,333,444,546,768};		public void test() {			//排序		Arrays.sort(test);				//二分查找		int result = binarySearch1(test,12);				System.out.println("index = "+result);	}		public int binarySearch0(int[] a,int key) {		return binarySearchImpl0(a,key,0,a.length-1);	}		public int binarySearch1(int[] a,int key) {		return binarySearchImpl1(a,key,0,a.length-1);	}		/*先用递归实现*/	private int binarySearchImpl0(int[] a,int key,int lowindex,int highindex) {		/*int[] a是经过排序的数组，通常是升序排列,如果key超出范围，直接返回，函数只处理在范围内的查找不到的异常*/		if( key > a[highindex] || key < a[lowindex] ) {			return -1;		}				if( lowindex > highindex ) {			return -1;		}				int midindex = (lowindex+highindex)>>>1;		if( key < a[midindex] ) {			return binarySearchImpl0(a,key,lowindex,midindex-1);		} else if( key > a[midindex] ) {			return binarySearchImpl0(a, key, midindex+1, highindex);		} else {			return midindex;		}				/*小结：		 * 1、递归法的好处是函数逻辑结构简单		 * 2、缺点是如果数组体量很大，可能会造成函数栈溢出		 *    制造栈溢出的方法：1、申请一个大的local变量  2、深度递归*/	}		/*使用循环实现*/	private int binarySearchImpl1(int[] a,int key,int lowindex,int highindex) {		int midindex = 0;		int low = lowindex;		int high = highindex;				/*循环截止条件：lowindex > highindex*/		while( low <= high ) {			midindex = (low+high) >>>1;						if( key < a[midindex] ) {				high = --midindex;			} else if( key > a[midindex] ) {				low = ++midindex;			} else {				return midindex;			}		}				return -1;	}}

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