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AtomicBoolean是java.util.concurrent.atomic包下的原子变量，这个包里面提供了一组原子类。其基本的特性就是在多线程环境下，当有多个线程同时执行这些类的实例包含的方法时，具有排他性，即当某个线程进入方法，执行其中的指令时，不会被其他线程打断，而别的线程就像自旋锁一样，一直等到该方法执行完成，才由JVM从等待队列中选择一个另一个线程进入，这只是一种逻辑上的理解。实际上是借助硬件的相关指令来实现的，不会阻塞线程(或者说只是在硬件级别上阻塞了)。

public class MainActivity extends AppCompatActivity {    private boolean isReadBufferThreadRunning = false;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        BarWorker bar1 = new BarWorker("bar1");        BarWorker bar2 = new BarWorker("bar2");        new Thread(bar1).start();        new Thread(bar2).start();    }    public  class BarWorker implements Runnable {        private  boolean exists = false;        private String name;        public BarWorker(String name) {            this.name = name;        }        @Override        public void run() {            if (!exists) {                try {                    TimeUnit.SECONDS.sleep(1);                } catch (InterruptedException e1) {                    // do nothing                }                exists = true;                Log.e("wangqi", name +"eat");                try {                    Log.e("wangqi", name +"working");                    TimeUnit.SECONDS.sleep(2);                } catch (InterruptedException e) {                    // do nothing                }                Log.e("wangqi", name +"leave");                exists = false;            } else {                Log.e("wangqi", name +"give up");            }        }    }}

备注说明：1、上面代码可以看出两个线程都会执行，会先执行完后bar1后再执行bar2

2020-01-11 16:28:41.637 11738-11764/com.zqc.myapplication E/wangqi: bar2eat2020-01-11 16:28:41.637 11738-11764/com.zqc.myapplication E/wangqi: bar2working2020-01-11 16:28:41.641 11738-11763/com.zqc.myapplication E/wangqi: bar1eat2020-01-11 16:28:41.641 11738-11763/com.zqc.myapplication E/wangqi: bar1working2020-01-11 16:28:43.638 11738-11764/com.zqc.myapplication E/wangqi: bar2leave2020-01-11 16:28:43.641 11738-11763/com.zqc.myapplication E/wangqi: bar1leave在这里插入代码片

二、使用AtomicBoolean

public class MainActivity extends AppCompatActivity {    private boolean isReadBufferThreadRunning = false;    private static AtomicBoolean exists = new AtomicBoolean(false);    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        AtomaticTest atomatic1 = new AtomaticTest("bar1");        AtomaticTest atomatic2 = new AtomaticTest("bar2");        new Thread(atomatic1).start();        new Thread(atomatic2).start();    }    public  class AtomaticTest implements Runnable {        private String name;        public AtomaticTest(String name) {            this.name = name;        }        @Override        public void run() {            if (exists.compareAndSet(false, true)) {                Log.e("wangqi", name +"=enter");                try {                    Log.e("wangqi", name +"=working");                    TimeUnit.SECONDS.sleep(2);                } catch (InterruptedException e) {                    // do nothing                }                Log.e("wangqi", name +"=leave");                exists.set(false);            } else {                Log.e("wangqi", name +"=give up");            }        }    }}

打印如下：

2020-01-11 16:57:29.711 22734-22763/com.zqc.myapplication E/wangqi: bar2=give up2020-01-11 16:57:29.711 22734-22762/com.zqc.myapplication E/wangqi: bar1=enter2020-01-11 16:57:29.712 22734-22762/com.zqc.myapplication E/wangqi: bar1=working2020-01-11 16:57:31.712 22734-22762/com.zqc.myapplication E/wangqi: bar1=leave

备注说明：在执行多个线程时，AtomicBoolean 中exists.set(false)设置为false则只会执行一个线程，这里使用了compareAndSet。这个方法主要两个作用1. 比较AtomicBoolean和expect的值，如果一致，执行方法内的语句。其实就是一个if语句 2. 把AtomicBoolean的值设成update，比较最要的是这两件事是一气呵成的，这连个动作之间不会被打断，任何内部或者外部的语句都不可能在两个动作之间运行