[Interview Question] The Structure of the Java Stack & Heap

Java Memory Structure

See JVM Structure and Principles

The Java Runtime Data Area we built to run the application is located in memory

• The PC Register, Native Method Stack, and Method areas are shared by all threads.

• Only the Stack and Heap regions are thread-specific

Structure of the Heap

Eden → Survivor → Old

The objects are moved in the above format, which is basically the order of creation.

The role of the Garbage Collector

• Eden: a place where Java objects are stored as soon as they are created.

• Survivor & Old: space where objects are moved based on their degree of reference

• Mark and Sweep: uses the Mark and Sweep algorithm.

Minor Garbage Collector

Responsible for moving the Eden and Survivor regions (Young Generation) based on object references if their memory exceeds the allowable amount.

Major Garbage Collector

Responsible for removing all unreferenced objects and reclaiming memory when the memory of the Old region (Tenured Generation) exceeds the allowable limit.

• Stops all threads except the one running the garbage collector during the deletion process ('Stop-The-World')

Structure of the Stack

Base Type + Local Variables + Parameters

In the case of a parameter, it is used in the form of a reference to an object in the Heap region with the object's address value.

→ If the parameter refers to a different object, the address value will only be different, and the object stored in the Heap will not disappear immediately! (Hold until the Major GC is executed)

Note

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