由于Unsafe类不是提供给用户程序调用的类(Unsafe.getUnsafe()的代码中限制了只有启动类加载器(Bootstrap ClassLoader)加载的Class才能访问它),因此,如果不采用反射手段,我们只能通过其他的Java API来间接使用它,如J.U.C包里面的整数原子类,其中的compareAndSet()和getAndIncrement()等方法都使用了Unsafe类的CAS操作。
* Simple thread-safe counter using the Java monitor pattern * *@authorBrian Goetz and Tim Peierls */@ThreadSafepublicfinalclassCounter{@GuardedBy("this")privatelongvalue=0;publicsynchronizedlonggetValue(){returnvalue; }publicsynchronizedlongincrement(){if(value == Long.MAX_VALUE)thrownewIllegalStateE...
atomic.AtomicInteger; 2 3public class SafeSequene{ 4 private value = new AtomicInteger(0); 5 //返回一个唯一的数值 6 public synchronized int getNext(){ 7 return value.incrementAndGet(); 8 } 9} 2) 如果各个状态变量之间存在依赖关系,并且存在复合操作,那么是非线程安全的。来看下面一个例子,...
Thread safety without synchronization Easy to implement Cons: Early creation of resource that might not be used in the application. The client application can’t pass any argument, so we can’t reuse it. For example, having a generic singleton class for database connection where client applicatio...
It is far easier to design a class to be thread-safe than to retrofit it for thread safety later. 设计一个线程安全的类要比事后为其添加线程安全性更容易。 这句话的意思是,在最初设计类的时候就考虑线程安全性要比在后期对其进行修改和添加线程安全性要容易得多。如果在最初的设计中就充分考虑了并发...
public class Clients { public static void main(String[] args) { //线程池 ExecutorService mExecutorService = Executors.newCachedThreadPool(); TicketServer mTicketServer = TicketServer.getInstance(); //线程的计数器 CountDownLatch mCountDownLatch = new CountDownLatch(1100); ...
VarHandle intHandle=MemoryHandles.varHandle(int.class,ByteOrder.nativeOrder()); 这里支持的类型就是基本类型,包括 byte、short、char、int、float、long、double。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 for(int i=0;i<25;i++){intHandle.set(segment,/* offset */i*4,/* value to write...
importjava.util.concurrent.ConcurrentLinkedDeque;publicclassConcurrentLinkedDequeExample{publicstaticvoidmain(String[]args){ConcurrentLinkedDeque<String>deque=newConcurrentLinkedDeque<>();// 在多线程环境下使用ConcurrentLinkedDeque进行读写操作// ...}} ...
communicate anything meaningful and even add some more confusion. Though these definitions can’t be ruled out just like that, because they are not wrong. But the fact isthey do not provide any practical help or perspective. How do we make adifference between a thread-safe class and an ...
类文件重新定义时(Class redefinition,比如热更新 or instrumentation)。 偏向锁的取消(Biased lock revocation)。 各种debug操作(比如: 死锁检查或者stacktrace dump等)。 然而,让所有线程都stop了以后才做的一些事情,让所有线程都到就近的safepoint停下来本身就需要较长的时间才能大家都停下来。而且让所有线程都停下来是...