Executor封装的四种线程池类型

た入场券 2022-02-13 07:31 241阅读 0赞

java中使用线程，核心走ThreadPooLExecutor  
Executor封装好了四种线程池类

1.newCachedThreadPool创建一个可缓存线程池，如果线程池长度超过处理需要，可灵活回收空闲线程，若无可回收，则新建线程。

package threadpool;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    public class demo1 {
    	public static void main(String[] args) {
    		ExecutorService threadpool = Executors.newCachedThreadPool();
    		for (int i = 0; i < 100; i++) {
    			int temp=i;
    			threadpool.execute(new Runnable() {
    				public void run() {
    					System.out.println("线程名"+Thread.currentThread().getName() +",i:"+ temp);
    				}
    			});
    		}
    	}
    
    }

执行结果，可以发现线程名很多都是有重复的。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70]

2.newFixedThreadPool 创建一个定长线程池，支持定时及周期性任务执行。

package threadpool;
    
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    public class demo1 {
    	public static void main(String[] args) {
    		// 设置最大线程数量
    		ExecutorService threadpool = Executors.newFixedThreadPool(3);
    		for (int i = 0; i < 10; i++) {
    			int temp = i;
    			threadpool.execute(new Runnable() {
    				public void run() {
    					System.out.println("线程名" + Thread.currentThread().getName() + ",i:" + temp);
    				}
    			});
    		}
    	}
    }

运行结果，发现最大的线程数为3  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70 1]

3.newScheduledThreadPool 创建一个定长线程池，支持定时及周期性任务执行

package threadpool;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    import java.util.concurrent.ScheduledExecutorService;
    import java.util.concurrent.TimeUnit;
    		ScheduledExecutorService threadpool = Executors.newScheduledThreadPool(3);
    		for (int i = 0; i < 10; i++) {
    			int temp = i;
    			threadpool.schedule(new Runnable() {
    				public void run() {
    					System.out.println("线程名" + Thread.currentThread().getName() + ",i:" + temp);
    				}
    			}, 3,TimeUnit.SECONDS);
    		}
    	}
    }

3秒后执行线程，展示不了效果

4.newSingleThreadExecutor 创建一个单线程化的线程池，它只会用唯一的工作线程来执行任务，保证所有任务按照指定顺序执行。

package threadpool;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    public class demo1 {
    	public static void main(String[] args) {
    		ExecutorService threadpool = Executors.newSingleThreadExecutor();
    		for (int i = 0; i < 10; i++) {
    			int temp = i;
    			threadpool.execute(new Runnable() {
    				public void run() {
    					System.out.println("线程名" + Thread.currentThread().getName() + ",i:" + temp);
    				}
    			});
    		}
    	}
    }

执行结果  
其实和单线程没什么差别，所有几乎不太会用这个。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70 2]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70]: /images/20220213/fd947e7477e949d5939f174d4bc957d5.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70 1]: /images/20220213/b439b8ae2cd542c0a48a95265e02d957.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDcxNDgwOA_size_16_color_FFFFFF_t_70 2]: /images/20220213/b8cf256ca0fd4cee8ba4e6f35875edff.png