The difference between synchronized and lock

1. Original composition

1. synchronized Yes, the keyword belongs to JVM level .monitorenter( The bottom is through monitor Object complete , Actually wait/notify And so on monitor Objects can only be called in synchronous blocks or methods wait/notify Other methods ).
2. Lock It's a concrete class (java.util.concurrent.locks.Lock) yes api Level lock

2. Usage method

1. synchronized There is no need for the user to release the lock manually , When synchronized After the code is executed, the system will automatically let the thread release the lock occupation .
2. ReentrantLock You need to release the lock manually. If there is no active release of the lock , It may lead to deadlock . need lock() and unlock() Method coordination try/finally Statement block to complete .

3. Whether waiting can be interrupted

1. synchronized Non interruptible , Unless an exception is thrown or normal operation is completed .
2. ReentrantLock interruptible , Method 1： Set supermarket method tryLock(long timeout, TimeUnit unit), Method 2：lockInterruptibly() Put it in the code block , call interrupt() Method can be interrupted

4. Is it fair to lock

1. synchronized Not fair lock
2. ReentrantLock Either way , Default fair lock , The constructor can pass in boolean value ,true Lock for fairness ,false Lock for unfairness

5. Lock binding multiple fields Condition

1. synchronized No,
2. ReentrantlLock It is used to wake up the threads that need to wake up in groups , Can wake up exactly , Not like it synchronized Either wake up one thread randomly or wake up all threads .