一篇文章带你从 JVM 理解 Java 中的线程安全

╰半夏微凉° 2022-12-28 06:29 170阅读 0赞

### 文章目录 ###

*   *  一、线程安全
     *  二、Java 语言中的线程安全
     *  三、线程安全的实现方法

## 一、线程安全 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmh1YWliZWlhbg_size_16_color_FFFFFF_t_70]  
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## 二、Java 语言中的线程安全 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmh1YWliZWlhbg_size_16_color_FFFFFF_t_70 2]  
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![在这里插入图片描述][2020121510464287.png]  
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执行结果：  
![在这里插入图片描述][20201215104911527.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmh1YWliZWlhbg_size_16_color_FFFFFF_t_70 8]  
![在这里插入图片描述][20201215105030865.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmh1YWliZWlhbg_size_16_color_FFFFFF_t_70 9]

## 三、线程安全的实现方法 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmh1YWliZWlhbg_size_16_color_FFFFFF_t_70 10]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmh1YWliZWlhbg_size_16_color_FFFFFF_t_70 11]  
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在 synchronized 能实现需求的情况下，优先考虑使用 synchronized 来进行同步

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmh1YWliZWlhbg_size_16_color_FFFFFF_t_70 14]  
![在这里插入图片描述][20201215132539321.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmh1YWliZWlhbg_size_16_color_FFFFFF_t_70 15]  
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具体的案例可参考：[一篇文章带你深入了解 volatile 与 Java 内存模型（JMM）][volatile _ Java _JMM]

public class VolatileTest { 
    
        public static AtomicInteger race = new AtomicInteger(0);
    
        public static void increase() { 
            race.incrementAndGet();
        }
    
        private static final int COUNT = 20;
    
        public static void main(String[] args) { 
            Thread[] threads = new Thread[COUNT];
            for (int i = 0; i < COUNT; i++) { 
                threads[i] = new Thread(new Runnable() { 
                    @Override
                    public void run() { 
                        for (int j = 0; j < 10000; j++) { 
                            increase();
                        }
                    }
                });
                threads[i].start();
            }
            System.out.println(Thread.activeCount());
            // while (Thread.activeCount() > 1) { 
            // System.out.println(Thread.activeCount());
            // Thread.yield();
            // }
            System.out.println(race);
        }
    }

![在这里插入图片描述][20201215144752457.png]  
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[volatile _ Java _JMM]: https://blog.csdn.net/nanhuaibeian/article/details/109697079
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