Chapter 7: Garbage Collection & Serialization

Automatic memory management and object persistence form the foundation of JVM runtime stability. Understanding Generational GC mechanics, production GC collector algorithms (G1, ZGC), memory leak identification, and secure object serialization guarantees resilient backend services.

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🧭 Subtopics & Curriculum

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Memory Management7.1

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7.1 Garbage Collection Fundamentals

• What is Garbage Collection?
• What exactly is "Garbage"?
• Why do we need Garbage Collection?
• Stack vs Heap
  • Stack contains :
  • Heap contains :
• How does Java know an object is unused?
• What are GC Roots?
• Does System.gc() perform Garbage Collection?
• Can we force Garbage Collection?
• How does Garbage Collection actually work?
• Generational Garbage Collection
  • Heap Division
  • Young Generation
  • Old Generation
• GC Phases (Steps of GC)
• Stop-The-World (STW)
  • Why is Stop-The-World a problem?

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Production Collectors7.2

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7.2 Types of Garbage Collectors

• 1. Evolution of HotSpot GC Collectors
• Serial Garbage Collector
• Parallel Garbage Collector
• G1 Garbage Collector
  • Why is G1 useful?
• ZGC
• Shenandoah GC
• Ways of Garbage Collection :
  • finalize() (Deprecated)
  • Try-with-resources — preferred
• AutoCloseable
• Cleaner

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Memory Leak7.3

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7.3 Memory Leak

• What is memory Leak in Java?
• Common causes of Memory Leaks
  • 1. Static collections
  • 2. Objects stored unnecessarily in caches
  • 3. Listeners/callbacks not removed
  • 4. ThreadLocal misuse
  • 5. Long-lived objects holding references to short-lived objects
• finalize() and Garbage Collection
• Can an object become eligible for GC without assigning null? ✅
• Can two objects reference each other and still be garbage? ✅
• What is OutOfMemoryError?
• Does OutOfMemoryError always mean a memory leak? ❌
• What is StackOverflowError?
• -Xms and -Xmx
  • -Xms
  • -Xmx

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Object Persistence7.4

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7.4 Serialization Fundamentals & UID

• What is Serialization?
• Why do we need Serialization?
  • 1. Store an object
  • 2. Transfer an object
• How do we serialize an object?
• Writing and Reading Streams
• What is serialVersionUID?

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Custom Serialization7.5

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7.5 Transient Fields & Custom Serialization

• What is Transient?
• Why use transient?
• Serialization vs Deserialization

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