How is Java Memory Structured and Managed?

Memory Management in Java

Java's memory allocation is divided into two main sections: the heap and the non-heap. The heap is the runtime data area from which the Java Virtual Machine (JVM) allocates memory for class instances and arrays. The non-heap includes memory required for internal processing and optimization for the JVM.

Heap Memory

The heap memory is further divided into three pools: Eden Space, Survivor Space, and Tenured Generation (Old Gen).

• Eden Space: Memory is initially allocated for most objects from the Eden Space pool.
• Survivor Space: Objects that survive the garbage collection of the Eden Space are moved to the Survivor Space.
• Tenured Generation: Objects that have existed for some time in the Survivor Space are moved to the Tenured Generation.

Non-Heap Memory

The non-heap memory includes two main pools: Permanent Generation and Code Cache.

• Permanent Generation: Contains all the reflective data of the JVM itself, such as class and method objects.
• Code Cache: Contains memory for compilation and storage of native code.

Monitoring Memory Usage

The Java Monitoring and Management Console (JConsole) provides a graphical user interface to monitor various aspects of a Java application, including memory usage. JConsole displays the memory usage of the heap and non-heap pools mentioned above, allowing developers to identify potential memory issues.

Additional Resources

• [Heap Memory in Java](https://docs.oracle.com/javase/8/docs/technotes/guides/vm/gctuning/fundamentals.html#memorymodel)
• [Non-Heap Memory in Java](https://docs.oracle.com/javase/8/docs/technotes/guides/vm/gctuning/fundamentals.html#noheapmemory)
• [Using JConsole](https://docs.oracle.com/javase/8/docs/technotes/tools/share/jconsole.html)

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