问题
I read some where that sometimes JVM will identify some objects and try to create it in stack than heap as the memory allocation on the stack is cheaper than the memory allocation in the heap, deallocation on the stack is free and the stack is efficiently managed by the run-time. So is how this object allocation in stack works and is there any way to force the JVM to do this ?
回答1:
There is no way to force the JVM to allocate objects anywhere. You should not care where Java actually allocates your Object because it is not defined in the specifications. That being said the JVM has gotten a lot smarter and using a technique called escape analysis it can, if it wants to, allocate an object on the stack. There is however no way to force the JVM to allocate an Object at a specific place and it is not required by the specification that this behavior happen.
回答2:
If talk about HotSpot JVM, it never allocates Java objects on a stack. However there is an optimization: when Escape Analysis can prove that an object reference does not escape the scope being compiled, JIT eliminates an allocation at all and replaces the object fields with the local variables.
Note: we cannot claim this an allocation on a stack since the object does not exist, e.g. calling Object's methods like hashCode or wait is not possible.
Whenever JVM can eliminate the allocation, it does so automatically.
If it cannot - there is no way to force it.
来源：https://stackoverflow.com/questions/25561759/is-it-possible-to-force-jvm-to-create-an-object-in-stack-other-than-heap