StackOverFlowError vs OutOfMemoryError in java

 StackOverflowError and OutOfMemoryError are both critical runtime errors in Java, but they originate from different memory regions and different causes.

🧨 1. StackOverflowError

java.lang.StackOverflowError occurs when the call stack (used for method calls and local variables) exceeds its limit.

💥 Cause:

Typically caused by deep or infinite recursion.

🔁 Example:

public class StackOverflowExample {
    public static void recursiveMethod() {
        recursiveMethod(); // Infinite recursion
    }

    public static void main(String[] args) {
        recursiveMethod();
    }
}

💣 2. OutOfMemoryError

java.lang.OutOfMemoryError occurs when the JVM cannot allocate memory for objects or operations because heap or other memory areas are full.

💥 Causes:

• Excessive object creation without garbage collection.

• Memory leaks (unreferenced objects not collected).

• Huge arrays, large images, or data.

• Misconfigured JVM memory (-Xmx, -XX:MaxMetaspaceSize).

🔁 Example:

import java.util.*;

public class OutOfMemoryExample {
    public static void main(String[] args) {
        List<int[]> list = new ArrayList<>();
        while (true) {
            list.add(new int[1_000_000]); // Keeps allocating memory
        }
    }
}




Feature
StackOverflowError
OutOfMemoryError




Package
java.lang.StackOverflowError
java.lang.OutOfMemoryError


Memory Area
Stack Memory (used for method calls and local variables)
Heap, Metaspace, Direct Memory, or Other JVM areas


Cause
Too deep or infinite recursion, or extremely large stack frames
Creating too many objects, memory leaks, or excessive class loading


Common Scenario
Recursive method without exit condition
Adding elements endlessly to a list, loading many classes, large arrays


Thread-specific
Yes (each thread has its own stack)
No (shared JVM memory like heap/Metaspace)


Thrown by JVM?
Yes
Yes


Recoverable?
Difficult; JVM will often terminate the thread
Sometimes recoverable if caught and memory is freed


Can be Caught?
Technically yes, but not practical
Yes, but rarely useful except for logging or controlled shutdown


🛠️ How to Resolve Each
✅ Resolving StackOverflowError



Action
Description




🔄 Fix recursive logic
Ensure all recursive calls have a base condition.


⬆️ Increase stack size
Use JVM flag -Xss (e.g., -Xss1m) to increase stack size.


🔃 Use iteration instead of recursion
For deeply recursive logic, convert recursion to iteration.


⚠️ Avoid large stack frames
Don't declare huge local variables or nested method calls unnecessarily.


✅ Resolving OutOfMemoryError

A. Java Heap Space

Action	Description
🧹 Optimize object usage	Avoid holding unnecessary objects.
🔄 Enable garbage collection logs	-verbose:gc or use VisualVM, JConsole to monitor GC.
⬆️ Increase heap size	Use -Xms and -Xmx (e.g., -Xmx1024m).
🔍 Use memory profilers	Detect memory leaks (e.g., VisualVM, Eclipse MAT).

B. Metaspace (Java 8+)

Action	Description
📦 Unload classes	Avoid classloader leaks (common in app servers, frameworks).
⬆️ Increase metaspace	Use -XX:MaxMetaspaceSize=256m.
🔄 Use shared classloaders	Reuse class loaders when possible.

C. GC Overhead Limit Exceeded

Action	Description
📈 Increase heap	-Xmx to give GC more room to work.
🧠 Fix memory leaks	Track down objects not being garbage collected.
💡 Optimize code	Avoid unnecessary object creation inside loops.

📂 JVM Options for Troubleshooting

Option	Purpose
-Xmx<size>	Set max heap size
-Xss<size>	Set stack size per thread
-XX:+HeapDumpOnOutOfMemoryError	Create memory dump on OOM
-verbose:gc	Print GC logs
-XX:MaxMetaspaceSize=256m	Limit metaspace

🧠 Summary

Aspect	StackOverflowError	OutOfMemoryError
Memory Area	Stack	Heap, Metaspace, etc.
Main Cause	Infinite recursion	Excessive memory use
Fix	Fix recursion or increase stack	Free up memory or increase limits
Tools	Increase -Xss, check code logic	VisualVM, -Xmx, memory profilers