java concurrency course

This article discusses several approaches to parallel processing in Java applications. From managing Java threads to a variety of other workarounds, executor services, Forkjoin frameworks, and actor models in calculations.4 styles of Java Concurrent Programming: Threads,executors,forkjoin and actorsWe live in a world where things happen in parallel. Naturally, th

Java concurrency: counters of thread synchronization mechanism Exechanger, java counters Section 1 CountDownLatch (1) first recognized CountDownLatch (2) Detail CountDownLatch CountDownLatch is implemented by a counter. The initial value of the counter is the number of threads. Every time a thread completes its own task, the counter value is reduced by 1. Wh

Java thread concurrency: knowledge point, java thread knowledge pointJava thread concurrency: knowledge point release: an object is used to make it be referenced by code out of the current range. Common form: store the reference of an object to a public static domain; A reference is returned in a non-private method. An

The safest way to add a new atomic operation is to modify the original class to support the desired operation. However, you may not have access to the source code or the freedom to modify it, so it is usually impossible. Even if you can modify the original class, you also need to understand its implementation of the synchronization strategy, in order to maintain the original design of the premise to improve its functionality. Adding a new method directly to a class means that all code that imple

First, the atomic natureAtomicity means that an operation is non-interruptible. Even when multiple threads are executing together, an operation will not be disturbed by other threads once it is started.i++是原子操作吗？不是，包含3个操作：读i,i=i+1,写i32位的机子上读取64位的long型也不是原子操作Second, the order of 2.1 examplesDuring concurrency, the execution of the program may occur in a disorderly sequence2.2 StepsThe execution of an instruction can be divided into a number of steps:

Why concurrency is requiredConcurrency is actually a decoupling strategy that helps us to separate what we do (the target) and when we do it (timing). Doing so can significantly improve the throughput of the application (getting more CPU scheduling time) and structure (multiple parts of the program are working together). As anyone who has ever done Java Web Development knows, the servlet program in the

shared variable, it reads directly from the main memory.Of course, synchronize and locks can guarantee visibility.Order of Ordering: The order in which the program executes is executed in the order of the Code. In the Java memory model, in order to be efficient, the compiler and processor are allowed to reorder instructions, and of course reorderin

Learn Java concurrency programming have to understand java.util.concurrent this package, this package has many of the concurrency tools we often use, such as: Reentrantlock, Countdownlatch, Cyclicbarrier, Semaphore and so on. The underlying implementations of these classes depend on the Abstractqueuedsynchronizer class, which shows the importance of this class. S

A period of time did not review multithreading related knowledge, although the work will use a number of multi-threaded content, but are biased to the foundation, today reread multi-threaded related content, found that some things still need attention. These are usually interview high-frequency problems. Understanding concurrency Insider is an indispensable course for a senior programmer

path and use the classes that have already been compiled. The premise is that you can find them, and JVM searches for classes through classpth. We need to set DT. jar and tools. jar in the Lib subdirectory under the JDK installation directory to classpath. Of course, the current directory "." must also be added to this variable.3. java_home environment variable. It points to the JDK installation directory. Eclipse, netbeans, tomcat, and other softwar

[Java concurrent programming] 9: deadlock (including code), java concurrency A deadlock may occur when the thread needs to hold multiple locks at the same time. Consider the following situations: Thread A currently holds the lock1 lock and thread B currently holds the lock2 lock. Next, when thread A still holds lock1, it tries to get lock2 because thread B is hol

);V.stopit ();Thread.Sleep (2000);SYSTEM.OUT.PRINTLN ("Finish main");System.out.println (V.getstop ());}Iv. Rules of Happen-beforeProcedural Order Principle: the serialization of semantics within a threadVolatile rules: The write of volatile variables, which occurs first in the read, which guarantees the visibility of volatile variablesLock rule: Unlocking (unlock) must occur before the subsequent locking (lock)Transitivity: A precedes b,b before C, then a must precede CThe start () method of th

In the previous few things about the Java memory model that basically explained the concept of the bottom of the domain, talk about high concurrency (35) Java memory model those things (iii) Understanding memory barriers This analysis of the X86 platform, Volatile,synchronized, CAS operations are implemented based on the assembly instructions of the lock prefix,

Java concurrency series [6] ---- Semaphore source code analysis, java ---- semaphore Semaphore is a common class in the JUC package. It is an application in the AQS sharing mode and allows multiple threads to operate on shared resources at the same time, in addition, it can effectively control the number of concurrent jobs and use it to control traffic. Semaphore

In this summary, we focus on the principle and design idea of atomic operation.Because of the locking mechanism in the next section, the concept of locking is introduced appropriately in this section.In the Java Concurrency in practice, this defines thread-safe: When multiple threads access a class, the behavior of the class is still correct , without regard to the scheduling and alternation of the

The Java memory model is the foundation for multi-threaded security, but the understanding of the cognitive type is not studied in depth.First, what is the memory model, why it needs its Java memory model (Java storage models) concurrency-related security announcements, synchronization policy specification, consistency

thread 1, thread 2 in the read,load operation, found that the value of count in main memory is 5, then the latest value will be loadedAfter the thread 1 heap count is modified, it is write to main memory, and the count variable in main memory becomes 6Thread 2 because the read,load operation has been performed, after the operation, the main memory will also be updated count of the variable value of 6When two threads are modified with the volatile keyword in a timely manner, there is still a

Java Open source Fresh e-commerce platform discussion and solution of concurrency problem and lock mechanism in-oms Order system (source code can be downloaded)Description: Discussion and solution of concurrency problem and lock mechanism in OMS order system of Java Open Source fresh e-commerce:Origin of the problemSup

() {Clear Business Full.notifyall ();}Think of more targeted object-oriented programming. Similar issues with databases: Dirty reads: The first thing reads the data that the second thing is updating, and if the UPDATE statement is not yet complete, the first thing reads only the data in a process, not the actual result. Oracle's Things by default: Read Committed (commit read), the problem does not occurExclusive Lock: Gets an exclusive lock when the data is changed.Shared Lock: The query acqui

Lock.lock mate Condition.await/signal provided by the concurrent package. Optimistic lock that the data will not be modified, so when the data are not locked, but in the back to write the data when the time to confirm whether someone updated this data, you can use the version number and other mechanisms. It can improve the throughput of the program if it is suitable for many read and write less. If write more is prone to data inconsistency caused retry, but inefficient. The implementation can b