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Introduction to Garbage Collection

In Java, Garbage Collection (GC) is the process by which Java programs perform automatic memory management.

When your Java program runs, it creates objects on the Heap. Over time, some of these objects will no longer be needed by the application. The Garbage Collector's job is to automatically find these unused objects and delete them to free up memory.

C/C++ vs Java Memory Management​

To truly appreciate Java's Garbage Collection, it helps to understand how memory was managed before Java existed.

The C/C++ Approach (Manual Memory Management)​

In languages like C and C++, the programmer is entirely responsible for both creating and destroying objects.

  • You allocate memory using functions like malloc().
  • When you are done with the object, you must manually free the memory using free().

The Problem: If a programmer forgets to call free(), the memory remains occupied forever, causing a Memory Leak. If a program leaks enough memory, it will eventually crash the entire system.

The Java Approach (Automatic Memory Management)​

Java designers decided that manual memory management was too error-prone. In Java:

  • You allocate memory using the new keyword.
  • You do not free the memory.

Instead, a special daemon thread called the Garbage Collector runs continuously in the background of the JVM (Java Virtual Machine). It constantly monitors the heap memory, identifies which objects are no longer being used by your application, and automatically destroys them.

[!NOTE] While Java's automatic Garbage Collection eliminates the need for manual free() calls, it does not mean Java is completely immune to memory leaks. If you keep holding references to objects you no longer need (like throwing them into a static HashMap and forgetting about them), the GC cannot destroy them!