Welcome to Java City — a place where objects live, work, and sometimes… get forgotten.
Every time you write:
new Employee("Shweta");
You’re actually building a house in Java City and moving someone in — in this case, Employee Shweta.
Thousands of such objects are created every day — Employees, Invoices, Strings, Lists…
And like every growing city, memory space is limited.
At first, everything is fine. Each object has a place to live.
But as developers build more features — more houses, more records, more data —
some objects get abandoned.
No one remembers them anymore.
No variable points to them.
They just… exist, taking up space, doing nothing.
🧍‍♂️ The Forgotten Citizens
An old UserSession that’s no longer active.
A temporary StringBuilder you used once.
A List from a method that already returned.
All these are forgotten citizens of Java City — still occupying homes, but no one knows they’re there.
Left unchecked, the city would soon run out of land —
and your program would crash with an OutOfMemoryError.
🧹 The Arrival of the Garbage Collector
That’s when the Garbage Collector (GC) arrives —
the silent janitor of Java City.
He walks through every street, checking:
“Is anyone still referencing this house?”
“Is there a variable or an object pointing here?”
If no one answers — the GC marks that house for demolition.
Later, it sweeps those homes away, freeing up land.
No ceremony. No drama. Just quiet cleanup.
⚙️ The GC’s Secret Art — Mark and Sweep
It’s not random destruction.
Mark phase:
The GC starts from roots (like active threads, static variables, and stack references).
Anything reachable from these roots gets marked as alive.
Sweep phase:
Every unmarked house is cleared — memory reclaimed.
This process keeps the city alive and thriving — without developers manually deleting anything.
💡 The Modern Twist — Different Neighborhoods
Java City has multiple zones:
Young Generation → Where new objects are born.
Old Generation → Where long-living ones settle.
Metaspace → Where class definitions live.
The GC behaves differently in each area:
Cleaning the young area often (minor collections) and the old one less frequently (major collections).
⚠️ When the GC Gets Overworked
Even the best janitor has limits.
If you keep creating new objects faster than GC can clean up —
he gets overwhelmed.
You’ll see pauses, lag, even stop-the-world events —
when the GC halts everything to catch up.
That’s when tuning memory, reducing object creation, and reusing resources become crucial.
đź’¬ The Moral
The Garbage Collector isn’t magic — it’s your ally.
It saves you from the chaos of manual memory management.
But if you overwork memory, even the best janitor can’t save your city.
So the next time your app slows down,
remember — somewhere inside Java City,
a tired GC is whispering…
“I’m cleaning as fast as I can.” 🧹
👩‍💻 About the Author
Shweta is a Technical Lead who explains backend and cloud concepts through simple, story-driven examples and real-world developer insights.
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