Concurrent Java 00 - 并发引论

并发的概念

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Java 并发模型

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JMM - Java Memory Model

image.png JMM - 重要的理论模型

Java 并发编码初体验

创建标记Annotation

package com.accat.concurrency.annoations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 用来标记【不推荐】的类或者写法
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.SOURCE)
public @interface NotRecommend {

    String value() default "";
}

package com.accat.concurrency.annoations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 用来标记【线程不安全】的类或者写法
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.SOURCE)
public @interface NotThreadSafe {

    String value() default "";
}

package com.accat.concurrency.annoations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 用来标记【线程不安全】的类或者写法
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.SOURCE)
public @interface NotThreadSafe {

    String value() default "";
}

package com.accat.concurrency.annoations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 用来标记【线程安全】的类或者写法
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.SOURCE)
public @interface ThreadSafe {

    String value() default "";
}

测试

package com.accat.concurrency;

import com.mmall.concurrency.annoations.NotThreadSafe;
import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

@Slf4j
@NotThreadSafe
public class ConcurrencyTest {

    // 请求总数
    public static int clientTotal = 5000;

    // 同时并发执行的线程数
    public static int threadTotal = 200;

    public static int count = 0;

    public static void main(String[] args) throws Exception {
        ExecutorService executorService = Executors.newCachedThreadPool();
        final Semaphore semaphore = new Semaphore(threadTotal);
        final CountDownLatch countDownLatch = new CountDownLatch(clientTotal);
        for (int i = 0; i < clientTotal ; i++) {
            executorService.execute(() -> {
                try {
                    semaphore.acquire();
                    add();
                    semaphore.release();
                } catch (Exception e) {
                    log.error("exception", e);
                }
                countDownLatch.countDown();
            });
        }
        countDownLatch.await();
        executorService.shutdown();
        log.info("count:{}", count);
    }

    private static void add() {
        count++;
    }
}