Heap Space

Java's Heap Space implementation.

Used to allocate memory to objects at run time

How is object stored in memory?

• The actual data/structure that is stored on the heap starts with what's commonly called object header.
• Header contains — a (compressed) class pointer
• Class pointer —> an internal data structure
• Internal data structure — defines layout of the class
• Layout of class — stored in a separate memory area called Metaspace (or Compressed Class space if Compressed OOPs are used).
• The pointer can be 4 or 8 bytes, depending on the architecture - even on 64-bit systems, it's usually 4 bytes due to the Compressed OOPs optimization.

References

• How references are stored in Java
• More about layout of java objects — Java Objects Inside Out
• Compressed OOPs

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Children

1. Program Counter Register

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Backlinks

• Objects lifecycle in memory (cs)