Runtime vs compile time memory allocation in java

Question

I am confused regarding whether memory allocation in java occurs at run time or compile time.

For example:

class Test{
  int a;
  public Test(){
             


        

Answer 1

Local variables and method parameters such as primitives or reference, are notionally allocated a place on the stack at compile time.

At runtime, this isn't guaranteed to to reflect how it is laid out in memory.

Allocation of objects on the heap only occurs at runtime.

how is it possible as java runs on VM which directly takes compile .class file.

Only the VM knows how the code will be compiled so it not possible to do memory allocation at compile time.

when is a assigned value 10

At the line where the assignment occurs. Given its not used, the JIT can discard it so it might no happen at all.

Also the same question stands for reference variable t.

t is assigned where the = is after the object is constructed.