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[] args) throws Exception { Executorservice Executorservice=executors.newfixedthreadpool (3); Future3 Execute multiple call methods simultaneously, return multiple return values, who first executes who first returnsPackage Com.lipeng;import Java.util.random;import Java.util.concurrent.callable;import Java.util.concurrent.completionservice;import Java.util.concurrent.executorcompletionservice;import Java.util.concurrent.executorservice;import Java.util.concurrent.executors;public class FutureAnd
Related articlesJava Concurrent Programming (i) Thread definitions, states, and propertiesJava concurrent Programming (ii) synchronizationJava Concurrency Programming (iii) volatile domainsPrefaceBefore we talked about threading, synchronization, and the volatile keyword, we need to understand Java's memory model for c
Java Concurrent Programming Series: Java concurrency Programming: core theory Java Concurrency Programming: synchronized and it
, but for 64-bit data types long and double, A loose rule is defined in the model that allows the virtual machine to divide the read and write operations of 64-bit data that are not volatile-modified into two 32-bit operations. Thus, if there are multiple threads sharing a long or double type of variable that is not declared volatile, and both are read and modified, some threads may read a value that is neither the original nor the other thread to modify the value that is worth representing the
used if the volatile variable can simplify the implementation of the Code and validate the synchronization policy. In general, it is more secure to use the synchronization mechanism.4, the locking mechanism (that is, the synchronization mechanism) can ensure both visibility and atomicity, and volatile variables can only ensure visibility, because a simple variable declared volatile if the current value is related to the previous value of the variable, then the volatile keyword does not work, I
the synchronization policy. In general, it is more secure to use the synchronization mechanism.4, locking mechanism (i.e. synchronization mechanism) can ensure both visibility and atomicity, and volatile variables can only ensure visibility, because simple variable declared volatile if the current value is related to the previous value of the variable, then the volatile keyword does not work, meaning the following expression is not an atomic operation: " count++ "," Count = count+1 ". You shoul
operations of lock, unlock, read, load, assign, use, store, and write are atomic, but for 64-bit data types long and double, A loose rule is defined in the model that allows the virtual machine to divide the read and write operations of 64-bit data that are not volatile-modified into two 32-bit operations. Thus, if there are multiple threads sharing a long or double type of variable that is not declared volatile, and both are read and modified, some threads may read a value that is neither the
canceled or fails, the calculation will indicate that the computation process has been canceled or failed. In order to resolve this situation, if Memoizer finds that the calculation was canceled or detected with RuntimeException, the future will be removed. Memoizer also does not address cache overdue issues, but can be resolved by using subclasses of Futuretask, specifying a time-out for each result in subclasses, and periodically scanning for overdue elements in the cache. Similarly, the cach
Java concurrency Programming: core theory Java Concurrency Programming: synchronized and its implementation principles Java concurrency
false. 6. Break rules. When a thread calls interrupt on another thread, it must be executed before the interrupt call is detected by the interrupted thread. 7. Finalizer rules. The constructor of the object must be completed before the finalizer of the object is started. 8. transitivity. If operation A is performed before action B, action B is performed before Operation C, then action A must be performed before Operation C. Double check lock
Java concurrency Programming, you need to know.Three elements of concurrent programming An atom of atoms, a particle that cannot be split again. In Java, the sub-nature refers to one or more operations that either execute successfully or all fail. The order in w
(); if NULL ) throw newsecurityexception ("Unsafe"); return Theunsafe;}Note The bold section of the code, which checks the class that calls the Getunsafe () function, and if the class's classloader is not NULL, throws the exception directly, rejecting the work. Therefore, this also makes it impossible for our own applications to use the unsafe class directly. It is an exclusive class used within the JDK.Note: Depending on how the Java
1th. Course Preparation1-1 Course Guidance1-2 Concurrent Programming First experience1-3 concurrency and high concurrency basic concepts2nd Chapter Concurrency Foundation2-1 CPU Multilevel Cache-cache consistency2-2 CPU Multi-level cache-Random order execution optimization2-3 Java
threadb resources, threadb waiting for Threada resources (here because of the synchronization method used, So the resource exactly refers to the object-level lock of the D1 and D2, which causes the deadlock. While there is no good way to avoid deadlocks in Java, it is useful to follow some rules in programming to minimize the occurrence of deadlocks: minimizing the scope of the lock, such as using a synchr
initializationSummary:Finally, the book is pretty much the same .... It's not easy to shout, but finally one more thing. This book probably now only understand about half, after all, only looked at once, poor translation quality for the book's reading added a lot of difficulty. In addition, the book theory is more than practice, the code practice is not much, the book has a lot of prerequisite knowledge is assumed you already know, so suitable for a certain basis of people to see. Later there i
is mainly two: Enhance the memory semantics of volatile. The old memory model allows volatile variables to be re-ordered with ordinary variables. JSR-133 strictly restricts the reordering of volatile variables and ordinary variables, so that volatile write-read and lock-release-fetches have the same memory semantics. Enhances final memory semantics. In the old memory model, the value of reading the same final variable multiple times may be different. To do this, JSR-133 added two r
section is in the Java 8 version, not the Java 5 version it was first introduced to. The design philosophy behind Atomicboolean is explained in the "Comparison and Exchange" section of my Java concurrency guide theme. Create a Atomicboolean You can create a atomicboolean li
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
[Why use concurrency ?]1. ImproveProgramRunning SpeedWhen running on a multi-core or multi-processor system, concurrent programs can take full advantage of multiple execution units to speed up; however, when running concurrent programs on a single processor, there are two scenarios: when there is a blocking in the Program (for example, I/O blocking), concurrency can increase the speed. If it is a CPU-consum
ConcurrenthashmapConcurrenthashmap is composed of the segment array structure and the HASHENTRY array structure.A concurrenthashmap contains a segment array, the structure of segment is similar to HashMap, is an array and a list structure, a segment contains a hashentry array, Each hashentry is an element of a linked list structure, and each segment guardian is an element of the Hashentry array, and when the data for the Hashentry array is modified, it must first obtain its corresponding segment
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