How does the Java virtual machine implement the “happen sooner” memory model?

Question

The Java memory model is based on a “happen-to” relationship, which applies the rules, but also allows you to optimize the implementation of the virtual machine in terms of cache invalidity.

For example, in the following case:

// thread A
private void method() {
   //code before lock
   synchronized (lockA) {
       //code inside
   }
}

// thread B
private void method2() {
   //code before lock
   synchronized (lockA) {
       //code inside
   }
}

// thread B
private void method3() {
   //code before lock
   synchronized (lockB) {
       //code inside
   }
}

if thread A calls method()and thread B tries to get lockAinside method2(), then to synchronize with, lockAit will be necessary for thread B to observe all the changes that thread A made for all its variables before releasing its lock, even the variables that were changed in the section "Code before locking "

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Answer 1

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Answer 2

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