Synchronized implementation and lock upgrade

1. How does the JVM process and identify Synchronized? We analyze the implementation of synchronized from the bytecode perspective: Synchronized (lock object) {}Synchronized code blockThe underlying implementation is the monitorenter and monitorexit instructions. When modifying ordinary synchronization methods, the underlying implementation is: The execution instruction will check whether the method is set ACC_SYNCHRONIZED. If it […]

Java Core 05-AQS&ReentrantLock&Synchronized and other lock principles

AQS(AbstractQueueSynchronizer) Overview of AQS principles AQS means abstract queue synchronizer. Lock and other concurrency tool classes under the JUC package are implemented based on it. AQS maintains a volatile-modified state variable and a CLH (FIFO) two-way queue. The core idea of AQS is that if the requested shared resource is idle, the thread currently requesting […]

synchronized and ReentrantLock

Overview The differences between synchronized and ReentrantLock are as follows: The pseudocode for the two lock usage methods is as follows: // **************************How to use Synchronized*************** *********** // 1. Used for code blocks synchronized (this) {<!– –>} // 2. Used for objects synchronized (object) {<!– –>} // 3. Used for methods public synchronized void test […]

The phenomenon of synchronized 8 locks

1, Standard access, please print the email or text message first? /** * Multi-threaded 8 locks * 1. For standard access, should I print the email or text message first? */ public class Lock8 { public static void main(String[] args) throws InterruptedException { Phone phone = new Phone(); new Thread(() -> { try { phone.sendEmail(); […]

Kill ThreadSupplement: The role of Synchronized

[Kill Thread] supplements: the role of Synchronized Detailed explanation of synchronize, lock upgrade 1. Introduction to Synchronized 1. The role of Synchronized Easy to understand: It can ensure that at most one thread executes this code at the same time to achieve the effect of ensuring concurrency safety. 2. Synchronized status 2. Two uses […]

synchronized and lock upgrade

synchronized Why every Java object can be used as a lock? No lock Code example: package multiThreads; import; public class SynchronizedTest {<!– –> public static void main(String[] args) {<!– –> Object o = new Object(); int hashCode = o.hashCode(); System.out.println(“Decimal hashCode:” + hashCode); System.out.println(“Hex hashCode:” + Integer.toHexString(hashCode)); System.out.println(“Binary hashCode:” + Integer.toBinaryString(hashCode)); System.out.println(ClassLayout.parseInstance(o).toPrintable()); System.out.println(“——-“); } […]

Concurrent programming – synchronized

Article directory Atomicity, orderliness, visibility atomicity Orderliness visibility synchronized use synchronized lock upgrade synchronized-ObjectMonitor Atomicity, orderliness, visibility Atomicity Atomicity of database transactions: It is the smallest unit of execution. Multiple operations of a transaction either succeed or fail. Atomicity of concurrent programming: one or more instructions do not allow interruption during CPU execution. i++;Is the […]

synchronized in Java: a brief analysis of characteristics, usage, locking mechanism and strategy

Directory Features of synchronized mutual exclusivity visibility Reentrancy How to use synchronized synchronized lock mechanism Common lock strategies Optimistic locking and pessimistic locking Heavyweight locks and lightweight locks Fair lock and unfair lock Reentrant locks and non-reentrant locks spin lock read-write lock Characteristics of synchronized Mutual exclusivity synchronized ensures that only one thread can enter […]