How garbage collection works in Java

Let me explain how garbage collection works in Java.

Garbage collection in Java is an automated memory management process that identifies and removes objects that are no longer being used. Here's how it works:

Identification of Garbage

1.Java uses a concept called "reachability" to identify garbage

2. Objects still referenced from:

Active threads

Static fields

Local variables in active methods are considered "reachable" and kept alive

3. Objects that can't be reached are marked as garbage

Generational Collection

Java divides the heap into different generations:

Young Generation (Eden Space + Survivor Spaces)

Old Generation (Tenured)

Metaspace (for class metadata)

Garbage Collection Process

Minor GC (Young Generation)

Most objects die young

Quick and efficient

survivors move to Survivor spaces

After surviving multiple cycles, objects promote to Old Generation

Major GC (Old Generation)

Less frequent but more thorough

Usually causes "Stop the World" events

More time-consuming

Common GC Algorithms

Serial GC (single thread)

Parallel GC (multiple threads)

MS (Concurrent Mark Sweep)

G1 GC (Garbage First)

ZGC (Z Garbage Collector)

Example of an object becoming eligible for garbage collection:

javaCopypublic void example() {

Student student = new Student(); // Object created

student = null; // Object becomes eligible for GC

// Or when method ends, local reference goes out of scope

}