存储在Scala中的AnyVal子类型在哪里？

Question

In Java, within a method when we create primitives they are stored in stack memory, while objects instantiated (like using new ) are put on heap. In scala, AnyVal 's subtypes(like Int ) are immutable value instances that can't be instantiated. So if I create an Int in a Scala method, does it go to heap or stack. I am asking it because in Scala Int is an object.

Answer 1

The Scala Language Specification does not say anything about how memory is organized. Every implementation is free to organize its memory however it wants.

By the way, your statements about Java are wrong:

In Java, within a method when we create primitives they are stored in stack memory,

There is nothing in the Java Language Specification which says that. And in fact, for many implementations, this isn't true. For example, Oracle JDK's implementation will try to store primitives in registers, or elide them completely, instead of storing them on the stack.

while objects instantiated (like using 'new') are put on heap.

Again, there is nothing in the Java Language Specification which says that. And again, for example in Oracle's implementation, this is not necessarily true. Oracle's optimizing compilers will perform Escape Analysis and allocate objects on the stack whenever possible, ie when the compiler can prove that the reference doesn't escape the scope. Azul's implementation always allocates objects on the stack (unless it can prove that the reference will definitely escape the local scope), and performs Escape Detection, ie when it detects a reference escaping the local scope, it will move the object from the stack to the heap.

In fact, you can implement Java without a stack at all, and be perfectly compliant with the Java Language Specification.

In scala, AnyVal's subtypes(like Int) are immutable value instances that can't be instantiated. So if I create an Int in a Scala method, does it go to heap or stack.

That depends on the implementation, the version, the specific circumstances, and many other things. The Scala Language Specification doesn't say one way or the other, in fact, it doesn't say anything about how to memory, let alone about stack and heap.

I am asking it because in Scala Int is an object.

But again, that doesn't say anything about how it is implemented. Scala-JVM, for example, implements scala.Int as a JVM primitive, and then simply "fakes" the methods.