The local variableresultseems unnecessary. But, it’s there to improve the performance of our code. In cases where the instance is already initialized (most of the time), the volatile field is only accessed once (due to “return result;” instead of “return instance;”). This can improve...
在Java中,最基本的互斥同步手段就是synchronized关键字,synchronized关键字经过编译之后,会在同步块的前后分别形成monitorenter和monitorexit这两个字节码指令,这两个字节码都需要一个reference类型的参数来指明要锁定和解锁的对象。如果Java程序中的synchronized明确指定了对象参数,那就是这个对象的reference;如果没有明确指定,...
无论如何,要编写一个多线程安全(Thread-safe)的程序是困难的,为了让线程共享资源,必须小心地对共享资源进行同步,同步带来一定的效能延迟,而另一方面,在处理同步的时候,又要注意对象的锁定与释放,避免产生死结,种种因素都使得编写多线程程序变得困难。 尝试从另一个角度来思考多线程共享资源的问题,既然共享资源这么困...
making the Singleton thread safe was to not have to deal with synchronization when handling it thus it's unlikely you need/want to synchronize on it. Also, if you want to use a monitor object, you can increase the speed by reducing the synchronized block (see FasterSingleton in the code)...
A variable may return unexpected results when multiple threads run in parallel. Here, we need athread-safecode to prevent deadlocks in Java. Example: Consider a bank where only one token counter is available for token distribution. The task here is to create aBankclass only when a customer ...
Here is the updated code that implements a thread-safe Singletonpatternin Java: In this implementation, theinstancevariable is declared asvolatileto ensure thatmultiple threadshandle the variable correctly when creating the instance. The double-checked locking mechanism is still used to ensure that only...
(as listed in the VM_OPS_DO macro here: http://hg.openjdk.java.net/jdk10/jdk10/hotspot/file/5ab7a67bc155/src/share/vm/runtime/vm_operations.hpp … (if I am not mistaken) require the operations to be carried out at a "safeppint", which the JVM places at its own discretion. ...
Java Code: importjava.util.concurrent.locks.Lock;importjava.util.concurrent.locks.ReentrantLock;publicclassBankAccount{privatedoublebalance;privateLocklock;publicBankAccount(){balance=0.0;lock=newReentrantLock();}publicvoiddeposit(doubleamount){lock.lock();try{balance+=amount;System.out.println("Deposit: ...
Exception in thread "Thread-1"java.lang.NumberFormatException: multiple points at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1082) at java.lang.Double.parseDouble(Double.java:510) at java.text.DigitList.getDouble(DigitList.java:151) ...
Make a method thread-safe – Method 2 In this particular counter example, we actually can makecount++atomic by using AtomicInteger from the package “java.util.concurrent.atomic”. importjava.util.concurrent.atomic.AtomicInteger;publicclassMyCounter{privatestaticAtomicInteger counter=newAtomicInteger(0);...