How does Garbage Collection work in Java?

Best Full Stack Java Training Institute in Hyderabad with Live Internship Program

Are yu aiming to build a strong foundation in software development and land your dream job in the IT industry? Look no further than Quality Thought, the best Full Stack Java training institute in Hyderabad, known for its industry-focused training and valuable live internship program.

Quality Thought’s Full Stack Java course is designed for both beginners and professionals who want to master the skills required to develop real-world web applications. The course covers everything from Core Java, Advanced Java, JDBC, Servlets, JSP, Spring, Spring Boot, Hibernate, to front-end technologies like HTML, CSS, JavaScript, Bootstrap, Angular, and React.

What makes this training truly effective is the live internship, which provides hands-on experience on real-time projects. Students work in a simulated industry environment, dealing with actual coding tasks, debugging, deployment, version control, and team collaboration. This practical exposure helps learners build confidence and problem-solving skills—critical assets in any software job.

Program Highlights:

Comprehensive Full Stack Java Curriculum

Real-Time Projects with Live Internship

Mentorship from Industry Experts

Daily Practice, Assignments & Project Work

Resume Preparation, Mock Interviews & Placement Assistance

Internship Certificate & Career Guidance

Whether you're a fresher just out of college or a working professional planning a career switch, Quality Thought offers the best platform to become a skilled Full Stack Java Developer. With a focus on practical learning and job readiness, many of our students are now placed in top IT companies across India.

Join Quality Thought today – Get trained, get certified, gain real-world experience, and step confidently into the IT industry!

🔑 What is Garbage Collection (GC)?

• In Java, objects are created on the heap memory.

• When an object is no longer reachable (no live reference points to it), it becomes garbage.

• The Garbage Collector (part of the JVM) automatically identifies and removes such unused objects to free memory.

👉 In simple terms: GC reclaims memory from objects you no longer need, so developers don’t have to manually delete them (like in C++).

🔑 How Garbage Collection Works

1. Object Creation

   • You create objects using new. They are stored in heap memory.

2. Reachability Analysis

   • The JVM checks if an object is reachable from “root” references:

     • Local variables in stack frames

     • Static fields

     • Active thread references

   • If an object cannot be reached, it is considered eligible for garbage collection.

3. Garbage Collection Process

   • The GC algorithm (like Mark-and-Sweep) typically runs in two phases:

     • Mark: Traverses objects and marks those that are reachable.

     • Sweep: Collects unmarked (unreachable) objects and reclaims memory.

4. Finalization (Deprecated)

   • Before removing an object, the GC may call its finalize() method (but this is unreliable and deprecated).

5. Memory Reclaimed

   • The unused memory is freed and made available for new objects.

🔑 GC Algorithms in JVM

Different JVMs use different collectors, for example:

• Serial GC → Simple, one-threaded (for small apps).

• Parallel GC → Uses multiple threads (default for many JVMs).

• CMS (Concurrent Mark Sweep) → Reduces application pause times.

• G1 (Garbage First) GC → Modern collector, balances throughput and low pause.

• ZGC, Shenandoah → Very low pause collectors for large heaps.

🔑 Advantages of GC

• No need for manual memory management.

• Prevents most memory leaks.

• Improves application stability.

🔑 Limitations of GC

• You cannot predict exactly when GC will run.

• Can cause stop-the-world pauses (though modern collectors minimize this).

• May not catch logical memory leaks (when objects are still referenced but not actually needed).

⚡ In short:

Garbage Collection in Java is an automatic memory management process. The JVM tracks objects, determines which are no longer reachable, and reclaims that memory using GC algorithms like Mark-and-Sweep. This reduces developer burden but can sometimes affect performance.

Read More :

What are the main features of Java?

What is the difference between final, finally, and finalize() in Java?

Visit  Quality Thought Training Institute in Hyderabad   

Get Direction: