线程池

线程池：其实就是一个容纳多个线程的容器，其中的线程可以反复使用，省去了频繁创建线程对象的操作，无需反复创建线程而消耗过多的资源
如果并发的线程数量很多，并且每个线程都是执行一个时间很短的任务就结束了，这样频繁创建线程就会大大降低系统的效率，因为频繁创建线程和销毁线程需要时间

线程池：JDK1.5之后提供的

java.util.concurrent.Executors是线程池的工厂类，用来生成线程池

Executors类中的静态方法：
　　static ExecutorService newFixedThreadPool(int nThreads)创建一个可重用固定线程数的线程池

　　参数：int nThreads：创建线程池中的线程数量

　　返回值：ExecutorService接口返回的是ExecutorService接口的实现类对象，我们可以使用ExecutorService接口接收（面向接口编程）

java.util.concurrent.Executors：线程池接口
　　sumbit(Runnale task)用来从线程池中获取线程，调用start方法，执行线程任务
　　void shutdown() 关闭销毁线程池的方法
线程池的使用步骤
　　1.使用线程池的工厂类Executors里边提供的静态方法newFixedThreadPool生产一个指定数量的线程池
　　2.创建一个类，实现Runnable接口，重写run方法，设置线程任务
　　3.调用ExecutorService中的方法sumbit，传递线程任务（实现类），开启线程，执行run方法
　　4.调用ExecutorService中的方法shutdown销毁线程池（不建议使用）

package com.shopping.test;

public class RunnableImplements implements   Runnable{
    //2. 创建一个类，实现Runnable接口，重写run方法，设置线程任务
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName() + "创建一个新的线程");
    }
}

package com.shopping.test;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ThreadPool {

    public static void main(String[] args) {
        //1. 使用线程池的工厂类Executors里边提供的静态方法`newFixedThreadPool`生产一个指定数量的线程池
        ExecutorService es = Executors.newFixedThreadPool(2);
        //3. 调用`ExecutorService`中的方法`sumbit`，传递线程任务（实现类），开启线程，执行run方法
        es.submit(new RunnableImplements());
        //线程池会一直开启，除非调用shutdown方法
        //使用完线程之后，会自动把线程归还给任务（实现类），线程可以继续使用
        es.submit(new RunnableImplements());
        es.submit(new RunnableImplements());

        //4. 调用`ExecutorService`中的方法shutdown销毁线程池（不建议使用）
        es.shutdown();
    }
}

输出：

pool-1-thread-1创建一个新的线程

pool-1-thread-1创建一个新的线程

pool-1-thread-2创建一个新的线程

"C:Program Filesjdk1.7.0_51injava.exe" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2018.2.4libidea_rt.jar=51850:C:Program FilesJetBrainsIntelliJ IDEA 2018.2.4in" -Dfile.encoding=UTF-8 -classpath "C:Program Filesjdk1.7.0_51jrelibcharsets.jar;C:Program Filesjdk1.7.0_51jrelibdeploy.jar;C:Program Filesjdk1.7.0_51jrelibextaccess-bridge-64.jar;C:Program Filesjdk1.7.0_51jrelibextdnsns.jar;C:Program Filesjdk1.7.0_51jrelibextjaccess.jar;C:Program Filesjdk1.7.0_51jrelibextlocaledata.jar;C:Program Filesjdk1.7.0_51jrelibextsunec.jar;C:Program Filesjdk1.7.0_51jrelibextsunjce_provider.jar;C:Program Filesjdk1.7.0_51jrelibextsunmscapi.jar;C:Program Filesjdk1.7.0_51jrelibextzipfs.jar;C:Program Filesjdk1.7.0_51jrelibjavaws.jar;C:Program Filesjdk1.7.0_51jrelibjce.jar;C:Program Filesjdk1.7.0_51jrelibjfr.jar;C:Program Filesjdk1.7.0_51jrelibjfxrt.jar;C:Program Filesjdk1.7.0_51jrelibjsse.jar;C:Program Filesjdk1.7.0_51jrelibmanagement-agent.jar;C:Program Filesjdk1.7.0_51jrelibplugin.jar;C:Program 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est-java-sdk-1.0.5.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibactivemq-camel-5.6.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibactivemq-pool-5.13.2.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibaspectjweaver-1.6.12.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibcommons-digester-1.6.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjavax.servlet-5.1.12.jar;F:workspacewyfshopping_backupWebRootWEB-INFliblucene-queries-3.5.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibqiniu-java-sdk-7.0.7.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibactivemq-protobuf-1.1.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibalipay-sdk-java-3.0.1.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibcommons-logging-1.0.4.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibcommons-logging-1.1.3.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibhibernate-annotations.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibhk2-locator-2.3.0-b05.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibactivemq-console-5.6.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjackson-databind-2.3.2.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjackson-databind-2.5.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjavax.inject-2.3.0-b05.jar;F:workspacewyfshopping_backupWebRootWEB-INFliblucene-analyzers-3.5.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFliburlrewritefilter-4.0.3.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibavalon-logkit-2.0.dev-0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibcommons-collections-1.2.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibhibernate-entitymanager.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjavax.persistence_2.0.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibmongo-java-driver-3.8.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibpoi-ooxml-3.13-20150929.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibcommons-fileupload-1.2.1.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibcommons-httpclient-3.0.1.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibehcache-terracotta-2.4.6.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjackson-jaxrs-base-2.3.2.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjavax.annotation-api-1.2.jar;F:workspacewyfshopping_backupWebRootWEB-INFliblucene-highlighter-3.5.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjackson-annotations-2.3.2.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjackson-annotations-2.5.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibaliyun-java-sdk-core-3.2.3.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibaliyun-java-sdk-live-2.6.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjersey-media-multipart-2.9.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibmysql-connector-java-5.0.5.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibspring-security-core-2.0.4.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibvalidation-api-1.1.0.Final.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibosgi-resource-locator-1.0.1.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibpoi-ooxml-schemas-3.12-beta1.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibhibernate-commons-annotations.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjersey-media-json-jackson-2.9.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibmysql-connector-java-5.1.37-bin.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibspring-data-redis-1.3.0.RELEASE.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibspring-data-redis-1.6.0.RELEASE.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibaopalliance-repackaged-2.3.0-b05.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibspring-security-core-tiger-2.0.4.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjackson-jaxrs-json-provider-2.3.2.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjackson-module-jaxb-annotations-2.3.2.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibaliyun-java-sdk-dysmsapi-1.0.0-SANPSHOT.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibgeronimo-j2ee-management_1.1_spec-1.0.1.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibjboss-archive-browsing-5.0.0alpha-200607201-119.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibcom.springsource.org.apache.commons.beanutils-1.7.0.jar;F:workspacewyfshopping_backupWebRootWEB-INFlibcom.springsource.org.apache.velocity.tools.view-2.0.0.beta3.jar" com.shopping.test.ThreadPoolpool-1-thread-1创建一个新的线程pool-1-thread-1创建一个新的线程pool-1-thread-2创建一个新的线程
Process finished with exit code 0