书上的例题

   判断用户输入的一个整数是否是在已知的数组中。程序如下：

import java.util.*;
public class exercise2 {
   public static void main(String args[]) {
	  int start = 0,end,middle;
	  int a[] = {12,45,67,89,123,-45,67};
	  int N = a.length;
	  for(int i=0;i<N;i++) {
		  for(int j = i+1;j<N;j++) {
			  if(a[j]<a[i]) {
				  int t = a[j];
				  a[j] = a[i];
				  a[i] = t;
			  }
		  }
	  }
	  Scanner scanner = new Scanner(System.in);
	  System.out.println("输入整数，程序判断该整数是否在数组中：");
	  int number = scanner.nextInt();
	  int count = 0;
	  end = N;
	  middle=(start+end)/2;
	  while(number!=a[middle]) {
		  if(number>a[middle]) 
			  start = middle;
		  
		  else if(number<a[middle]) 
			  end = middle;
			  middle = (start+end)/2;
			  count++;
		  
		  if(count>N/2) 
			  break;
	  }
		  if(count>N/2) 
			  System.out.printf("%d不在数组中.\n",number);
		  
		  else 
			  System.out.printf("%d在数组中.\n",number);
		  
	  }
	   }