java通过Executors创建多线程

今天药忘吃喽~ 2021-09-25 06:18 249阅读 0赞

# java 线程池创建多线程 #

多线程开发，我这里就不说理论直接上代码。  
java通过Executors可以创建五种方式的对线程：  
第一种： 创建一个单线程。  
第二种： 创建一个可变的多线程。：  
第三种： 创建一个固定线程数的多线程。  
第四种：创建一个定时的多线程。  
第五种：创建可以调参数的多线程。

## 四种线程的创建方式： ##

//创建固定的线程池
            executorService = Executors.newFixedThreadPool(THREAD_SIZE);
            //创建可变线程池
            executorService = Executors.newCachedThreadPool();
            //创建单个线程池
            executorService = Executors.newSingleThreadExecutor();
            //创建固定时间的线程池
            executorService = Executors.newScheduledThreadPool(10);
          //线程池调优
            int corePoolSize = 2;         //核心线程数
            int maximumPoolSize = 5;      //最大线程数
            long keepAliveTime = 10L;     //线程存活时间
            TimeUnit unit = TimeUnit.SECONDS;
            executorService = new ThreadPoolExecutor(corePoolSize,
                    maximumPoolSize,
                    keepAliveTime,
                    TimeUnit.SECONDS,
                    new SynchronousQueue<Runnable>());

package com.util.multithreaduploadfile.util.multiThread;
    
    /**
     * @author ：柳浪涛
     * @packagename：com.util.multithreaduploadfile.util.multiThread
     * @date ：2021/3/24 11:30
     * @modified By ：
     * @version： 1.0
     * @Email： llt@echase.cn
     * @description： 固定线程池操作
     **/
    
    import org.apache.log4j.Logger;
    import org.apache.tools.zip.ZipEntry;
    
    import java.io.BufferedInputStream;
    import java.text.SimpleDateFormat;
    import java.util.*;
    import java.util.concurrent.*;
    
    
    public class FixedThreadPool {
    
        private static final Logger log = Logger.getLogger(FixedThreadPool.class);
        private static final int THREAD_SIZE = 7;
    
        public static Map<String, String> unzip(String key) throws Exception {
    
            //解压，不支持包含文件夹
            ZipEntry entry = null;
            BufferedInputStream bis = null;
            ExecutorService executorService = null;
            ConcurrentHashMap<String, String> resultMap = new ConcurrentHashMap<String, String>();
            try {
                //创建固定的线程池
                executorService = Executors.newFixedThreadPool(THREAD_SIZE);
            
             
    
                CompletionService<String> ecs = new ExecutorCompletionService<String>(executorService);
                List<Callable<String>> all = new ArrayList<>();
                for (int i = 0; i < 20; i++) {
                    UploadImage uploadImage = new UploadImage(resultMap, "name" + i, key);
                    Future<String> submit = ecs.submit(uploadImage);
                    SimpleDateFormat simple = new SimpleDateFormat("yyyy-MM-dd hh:ss:mm");
                    all.add(uploadImage);
                    System.out.println("==========前==========" + simple.format(new Date()));
                    //这里发生了阻塞
    //              System.out.println("==========take==========" +ecs.take().get());
                    System.out.println("==========后==========" + simple.format(new Date()));
                }
                System.out.println("=======多线程后面===========");
                //在这里阻塞
                //所有的线程执行完了才会执行下面的这里
                List<Future<String>> futures = executorService.invokeAll(all);
    
                if (futures != null && futures.size() > 0) {
                    for (Future<String> future : futures) {
                        System.out.println(future.get());
                    }
                }
                System.out.println("=======多线程后面===========");
                //只有通过execute提交的任务才能将它抛出的异常交给未捕获的异常处理器，
                // 而通过submit提交的任务，无论是抛出的未检查的异常，还是已检查的异常，
                //都将被认为是任务返回状态的一部分。如果一个由submit提交的任务由于抛出异常而结束，
                // 那么这个异常将被Future.get封装在ExecutionException中重新抛出
            } catch (Exception e) {
                System.out.println("====== 2 ====== " + e.getMessage());
                return null;
            } finally {
                executorService.shutdown();
                if (bis != null) {
                    bis.close();
                }
            }
            return resultMap;
        }
    
        static class UploadImage implements Callable<String> {
            private ConcurrentHashMap resultMap;
            private String imgName;
            private byte[] imgBytes;
            private String key;
    
            public UploadImage(ConcurrentHashMap resultMap, String imgName, String key) {
                this.resultMap = resultMap;
                this.imgName = imgName;
                this.key = key;
            }
    
            @Override
            public String call() {
                System.out.println();
                System.out.println("========imgName()======" + imgName);
                System.out.println("========线程编号======" + Thread.currentThread().getId());
    
    
                Random ran = new Random();
                try {
                    Thread.sleep(100);
                } catch (Exception ex) {
                    System.out.println("现场报错" + ex.getMessage());
    
                }
    
                return imgName;
            }
        }
    
    
        public static void main(String[] args) {
            try {
                FixedThreadPool.unzip("012");
            } catch (Exception EX) {
                System.out.println(String.format("%s%s", "========错误==========", EX.getMessage()));
    
            }
    
        }
    }

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对于没有使用过Executors来创建多线程的，这个是一个特别好的例子。  
mvn 的pom.xml附件

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.4.4</version>
            <relativePath/> 
        </parent>
        <groupId>com.util.multi.thread.upload.file</groupId>
        <artifactId>multithread-uploadfile</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>multithread-uploadfile</name>
        <description>Demo project for Spring Boot</description>
        <properties>
            <java.version>1.8</java.version>
        </properties>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-devtools</artifactId>
                <scope>runtime</scope>
                <optional>true</optional>
            </dependency>
    
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                 <version>1.18.12</version>
            </dependency>
    
            
            <dependency>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
                <version>1.2.17</version>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
    
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>8.0.20</version>
            </dependency>
    
            
            <dependency>
                <groupId>io.springfox</groupId>
                <artifactId>springfox-swagger2</artifactId>
                <version>2.9.2</version>
            </dependency>
            <dependency>
                <groupId>io.springfox</groupId>
                <artifactId>springfox-swagger-ui</artifactId>
                <version>2.9.2</version>
            </dependency>
    
            <dependency>
                <groupId>commons-io</groupId>
                <artifactId>commons-io</artifactId>
                <version>2.4</version>
            </dependency>
    
            
    
            
                
                
                
                
            
    
            
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>fastjson</artifactId>
                <version>1.2.62</version>
            </dependency>
    
            
                
                
                
            
    
            
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>2.1.3</version>
            </dependency>
    
            
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid-spring-boot-starter</artifactId>
                <version>1.1.23</version>
            </dependency>
    
            <dependency>
                <groupId>org.apache.ant</groupId>
                <artifactId>ant</artifactId>
                <version>1.10.5</version>
            </dependency>
    
    
            <dependency>
                <groupId>org.apache.commons</groupId>
                <artifactId>commons-lang3</artifactId>
                <version>3.12.0</version>
            </dependency>
    
            <dependency>
                <groupId>com.jd.utils</groupId>
                <artifactId>utils-common</artifactId>
                <version>2.0.1.RELEASE</version>
            </dependency>
    
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                    <configuration>
                        <excludes>
                            <exclude>
                                <groupId>org.projectlombok</groupId>
                                <artifactId>lombok</artifactId>
                            </exclude>
                        </excludes>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    
    </project>

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