【Java高并发学习】Java并行搜索，

Java并行搜索

1.二分查找（有序数组）

/**
 * 有序数组之二分查找
 * @author wsz
 * @date 2018年1月3日
 */
public class Demo {
	//数组以及数据
	static int[] arr= {25,48,65,87,123,233,456,666,777,8999,55555};
	//二分查找返回下标
	static int search(int[] arr,int target) {
		int len = arr.length;
		//中间、开始、结束下标
		int mid,low,high;
		low = 0;
		high = len-1;
		while(low <= high) {
			mid = (low+high)/2;
			if(arr[mid] == target) 
				return mid;
			else if(arr[mid] > target)
				high = mid-1;
			else
				low = mid+1;
		}
		return -1;
	}
	public static void main(String[] args) {
		int search = search(arr,666);
		System.out.println(search);
	}
}

2.并行搜索（无序数组）

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.atomic.AtomicInteger;
/**
 * 并行搜索：查找数组中数据，返回位置下标；没有则返回-1
 * @author wsz
 * @date 2018年1月3日
 */
public class Test implements Callable<Integer>{
	//该类实现Callable接口
	private int begin,end,search;
	
	public Test( int search,int begin, int end) {
		super();
		this.search = search;
		this.begin = begin;
		this.end = end;
	}

	@Override
	public Integer call() throws Exception {
		return search(search,begin,end);
	}
	
	//定义查询数据数组
	static int[] arr= {1,5,4,879,456465,1321,564,8798,154,45646,132,1321,48,7,87,8,8,7,87,98,89,546,46};
	//线程池+线程数量+存放结果变量result
	static ExecutorService pool = Executors.newCachedThreadPool(); 
	static final int THREAD_NUM =2;
	static AtomicInteger result = new AtomicInteger(-1);
	
	public static int search(int search, int begin,int end) {
		int i = 0;
		for(i = begin; i<end ;i++) {
			if(result.get() > 0) 	//判断其他线程是否已经得到结果，已得到则返回
				return result.get();
			
			if(arr[i] == search) {	//当前线程得到结果
				if(!result.compareAndSet(-1, i)) //使用CAS操作保存结果，如果失败则其他线程已先一步获取到结果。
					return result.get();
				return i;
			}
		}
		return -1;	//没有找到则返回-1
	}

	public static int pSearch(int search) throws InterruptedException, ExecutionException {
		int subArrSize = arr.length /THREAD_NUM+1;  //根据线程数对数组arr划分
		List<Future<Integer>> re = new ArrayList<Future<Integer>>();
		for(int i = 0; i<arr.length ; i+= subArrSize) {
			int end = i+subArrSize;
			if(end >= arr.length) end = arr.length;
			re.add(pool.submit(new Test(search,i,end)));//划分后，建立任务、提交查找、保存结果
		}
		for (Future<Integer> future : re) {
			if(future.get() >= 0)	  //如果不为-1，则找到结果并返回
				return future.get();
		}
		return -1;
	}
	
	public static void main(String[] args) throws InterruptedException, ExecutionException {
		int pSearch = pSearch(46);   //返回位置下标22
//		int pSearch = pSearch(460);  -1即没有找到
		System.out.println(pSearch);
	}
}