What is Garbage Collection in Java
💡 Concept: Garbage Collection in Java
Garbage Collection (GC) in Java is an automatic memory management process that identifies and frees up memory occupied by objects no longer in use.
📘 Quick Intro
GC helps prevent memory leaks and optimizes memory usage by reclaiming unused objects during runtime.
🧠 Analogy
Think of garbage collection as a janitor cleaning unused files and trash to free up space, so the system stays tidy and efficient.
🔧 Technical Explanation
- GC runs on the JVM and manages heap memory automatically.
- Detects unreachable objects by tracing references.
- Common algorithms: Mark-and-Sweep, Generational GC.
- Generational GC divides heap into young and old generations.
- Helps improve application performance by reclaiming unused memory.
🎯 Use Cases
- ✅ Automatic memory management in Java applications.
- ✅ Preventing memory leaks and out-of-memory errors.
- ✅ Optimizing long-running server applications.
💻 Example: Suggesting Garbage Collection
public class GCDemo {
public static void main(String[] args) {
GCDemo obj = new GCDemo();
obj = null; // Eligible for GC
System.gc(); // Request JVM to run GC
System.out.println("GC requested");
}
}
❓ Interview Q&A
Q1: What is garbage collection?
A: Automatic memory management in Java.
Q2: How does GC identify unused objects?
A: By tracing object references.
Q3: What are common GC algorithms?
A: Mark-and-Sweep, Generational GC.
Q4: Can you force garbage collection?
A: You can request it using System.gc(), but JVM decides when to run.
Q5: What is generational GC?
A: Heap divided into young and old generations for efficiency.
Q6: Does GC guarantee immediate memory reclaim?
A: No, it is up to JVM scheduling.
Q7: Can GC cause performance overhead?
A: Yes, during GC cycles.
Q8: What is memory leak in Java?
A: When unreachable objects are not garbage collected.
Q9: Is GC automatic in Java?
A: Yes, managed by JVM.
Q10: How to optimize GC?
A: By tuning JVM and managing object lifecycles properly.
📝 MCQs
Q1. What is garbage collection in Java?
- Manual memory management
- Automatic memory management
- Garbage creation
- None
Q2. How does GC identify unused objects?
- Counting references
- Tracing references
- Random
- Manual marking
Q3. What are common GC algorithms?
- Mark-and-Sweep, Generational
- Reference counting
- Copying
- None
Q4. Can you force garbage collection?
- Yes
- No, only request
- Always
- Sometimes
Q5. What is generational GC?
- Heap merged
- Heap divided for efficiency
- Stack only
- None
Q6. Does GC guarantee immediate reclaim?
- Yes
- No
- Sometimes
- Always
Q7. Can GC cause overhead?
- No
- Yes
- Maybe
- Never
Q8. What is memory leak?
- Unused memory
- Unreachable objects not collected
- Garbage data
- None
Q9. Is GC automatic?
- Yes
- No
- Sometimes
- Never
Q10. How to optimize GC?
- Ignore
- Tune JVM and object lifecycle
- Increase memory
- None
💡 Bonus Insight
Effective garbage collection management is crucial for performance in large-scale Java applications.
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