可实时调整运行中的线程个数

今天药忘吃喽~ 2022-04-03 09:38 154阅读 0赞

![1358476889_6912.jpg][]

import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.IOException;
    import java.util.Iterator;
    import java.util.List;
    import java.util.concurrent.Callable;
    import java.util.concurrent.ConcurrentLinkedQueue;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    import java.util.concurrent.Future;
    import java.util.concurrent.TimeUnit;
    
    import org.apache.commons.io.IOUtils;
    public class PDFTool2 {
    	private final static Integer ThreadNum = 3;
    	private final static ExecutorService exec = Executors.newCachedThreadPool();//创建线程池
    	public static void main(String[] args) throws Exception {
    		
    		//存放结果的队列
    		ConcurrentLinkedQueue<Future<Integer>> queue = new ConcurrentLinkedQueue<Future<Integer>>();
    		runDaemon(queue);
    		for(int i=0; i<ThreadNum; i++){
    			Future<Integer> future = exec.submit(getTask());
    			queue.add(future);
    		}
    	}
    	//运行后台线程,用于控制线程个数
    	public static void runDaemon(final ConcurrentLinkedQueue<Future<Integer>> queue){
    		Thread thread = new Thread(new Runnable(){
    			public void run() {
    				while(true){
    					try {
    						TimeUnit.SECONDS.sleep(5);//10秒监听一次
    					} catch (InterruptedException e) {e.printStackTrace();}
    					int UserThreadNum = getUserThreadNum();//用户输入的线程个数
    					int CurrentThreadNum = queue.size();//当前的线程个数
    					System.out.println("监听线程启动:当前有"+CurrentThreadNum+"个线程."+(UserThreadNum>0?"用户输入了"+UserThreadNum+"个线程.":""));
    					
    					if(UserThreadNum > CurrentThreadNum){//添加几个线程
    						for(int i=0; i<(UserThreadNum-CurrentThreadNum); i++){
    							Future<Integer> future = exec.submit(getTask());
    							queue.add(future);
    							System.out.println("添加了一个任务-------------------------");
    						}
    					}else if(UserThreadNum < CurrentThreadNum){//关闭几个线程
    						for(int i=0; i<(CurrentThreadNum-UserThreadNum); i++){
    							Future<Integer> future = queue.poll();
    							if(future != null){
    								boolean isSucc = future.cancel(true);//该任务被取消
    								System.out.println("取消了一个任务-------------------------"+isSucc);
    							}
    						}
    					}
    					//如果任务中有完成的,则把它踢出队列中
    					Iterator<Future<Integer>> iter = queue.iterator();
    					boolean isComp = false;
    					while(iter.hasNext()){
    						Future<Integer> future = iter.next();
    						if(future!=null && future.isDone()){
    							boolean isRemove = queue.remove(future);
    							System.out.println("一个任务已经完成,被移除.........."+isRemove);
    							isComp = true;
    						}
    					}
    					if(!isComp){System.out.println("没有一个任务已完成............");}
    				}
    			}}
    		);
    		thread.setDaemon(true);//设为后台线程
    		thread.start();
    	}
    	//获得用户输入的线程个数
    	public synchronized static int getUserThreadNum(){
    		int ThreadNum = 0;
    		String path = PDFTool1.class.getClassLoader().getResource("").getPath().replace("bin/", "");
    		path += "src/pdf/ThreadNum.txt";
    		try {
    			List<String> list = IOUtils.readLines(new FileInputStream(path));
    			if(list != null && list.size() > 0){
    				ThreadNum = Integer.parseInt(list.get(0));
    			}
    		} catch (FileNotFoundException e) {e.printStackTrace();
    		} catch (IOException e) {e.printStackTrace();
    		} catch (Exception e) {e.printStackTrace();}
    		return ThreadNum;
    	}
    	//获得任务
    	public static Callable<Integer> getTask(){
    		Callable<Integer> task = new Callable<Integer>(){
    			public Integer call() throws Exception {
    				process();
    				return 0;
    			}
    		};
    		return task;
    	}
    	//处理过程
    	public static void process(){
    		try {
    			TimeUnit.SECONDS.sleep(3);
    			System.out.println(Thread.currentThread().getName()+"完成.");
    		} catch (InterruptedException e) {
    //			e.printStackTrace();
    			return;//如果线程被interrupt,那么终止该线程
    		}
    		process();
    	}
    	/**
    	 * 运行结果：
    	 *  pool-1-thread-3完成.
    		pool-1-thread-1完成.
    		pool-1-thread-2完成.
    		监听线程启动:当前有3个线程.用户输入了2个线程.
    		取消了一个任务-------------------------true
    		没有一个任务已完成............
    		pool-1-thread-3完成.
    		pool-1-thread-2完成.
    		pool-1-thread-3完成.
    		pool-1-thread-2完成.
    		监听线程启动:当前有2个线程.用户输入了2个线程.
    		没有一个任务已完成............
    		pool-1-thread-2完成.
    		pool-1-thread-3完成.
    		pool-1-thread-3完成.
    		pool-1-thread-2完成.
    		监听线程启动:当前有2个线程.用户输入了5个线程.
    		添加了一个任务-------------------------
    		添加了一个任务-------------------------
    		添加了一个任务-------------------------
    		没有一个任务已完成............
    		pool-1-thread-3完成.
    		pool-1-thread-2完成.
    		pool-1-thread-1完成.
    		pool-1-thread-4完成.
    		pool-1-thread-5完成.
    	 */
    }

[1358476889_6912.jpg]: https://img-my.csdn.net/uploads/201301/18/1358476889_6912.jpg