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Does Java volatile prevent write caching or forced caching?

I am trying to understand the Java keyword volatilein relation to spelling for a volatile atomic variable in a multi-threaded program with processor caches.

I have read several guides and the Java language specification, in particular section 17.4.5 on “happens before ordering” . I understand that when a thread writes a new value to a volatile variable, the updated value should be visible to other threads reading this variable. For me, this semantics can be implemented in one of two ways:

  • Themes can cache a volatile variable in the CPU cache, but writing to the variable in the cache should be immediately deleted to main memory. In other words, write-through cache .

  • Threads can never cache a mutable variable and must read and write such variables in main memory.

Approach 1 is mentioned in this tutorial ( http://tutorials.jenkov.com ), which states:

By declaring a volatile counter variable, all records on the counter variable will immediately be returned to main memory.

Approach 2 is mentioned in the Stackoverflow question “ Variable Variable in Java ” as well as this tutorial , which says:

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