Memory Leaks in Java

Memory leaks in Java occur when objects that are no longer needed remain referenced, preventing garbage collection. Over time, this increases memory usage, degrades performance, and can eventually crash the application.

• Java provides automatic garbage collection, but it cannot remove objects that are still referenced.
• Poor reference management is the main reason memory leaks occur in Java applications.

Example: Memory Leak Due to Unused Objects

Finished adding items!

Explanation:The static list keeps all added items in memory, so even unused objects cannot be garbage collected, causing a memory leak.

Working of Memory Management in Java

• Java has automatic garbage collection, which simply means that Java can automatically free up memory for objects that are no longer in use or no longer needed.
• But if our program creates many objects but keeps references to them even if they are not needed, the garbage collector cannot destroy those objects. If memory use grows beyond the allowed limit, the program will crash.

Note: If an object is no longer needed, it is important to remove references to it so the garbage collector can free its memory.

Why Do Memory Leaks Happen in Java?

Even though Java has automatic garbage collection, memory leaks can occur when the program keeps references to objects that are no longer needed, preventing their removal and wasting memory.

Output:

Explanation:The program creates 1 MB arrays and stores them in a list. Because the list retains references, the garbage collector cannot free the memory, eventually filling the heap and causing an OutOfMemoryError.

Tools to Find Memory Leaks

There are multiple tools that help us to detect memory leaks by showing which object is using the most memory, and the list of such tools are listed below:

• VisualVM (comes with JDK)
• Eclipse Memory Analyzer (MAT)
• Java Mission Control
• YourKit Java Profiler

What Happens If Memory Keeps Leaking?

If our program keep on leaking memory it means the program will use up all the memory as much as it can use. After some time, the program will stop working and will show an error like this:

java.lang.OutOfMemoryError: Java heap space

This means Java ran out of memory to create new things it needs.

How to Avoid Memory Leaks?

We can avoid memory leaks by keeping few things in our mind which is listed below:

• Stop keeing things that we do not need in our program do not initialize unnecessary variables and list items to null.
• Do not let lists or caches keep growing forever without removing old stuff.
• It is always recommended to close files and database connections when we are done with them.

Memory Management in C vs Java