How Can I Calculate Total Memory Used and Total Free Memory in Java?

Understanding Runtime.getRuntime().totalMemory(), freeMemory(), and maxMemory()

Runtime.getRuntime().getTotalMemory() returns the total memory available to the Java Virtual Machine (JVM). This includes the memory occupied by objects, the Java heap, and other JVM structures. It does not represent the total memory used by your process.

Runtime.getRuntime().freeMemory() returns the amount of memory that is currently free and available for object allocation. It does not represent the total free memory available to the process.

Runtime.getRuntime().maxMemory() returns the maximum amount of memory that the JVM can allocate. This is typically set by the -Xmx command-line parameter.

Calculating Total and Used Memory

To determine the total amount of memory used by your process, you need to subtract the free memory from the total memory:

usedMemory = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();

Calculating Total Free Memory

To determine the total amount of free memory available to your process, subtract the used memory from the maximum memory:

freeMemory = Runtime.getRuntime().maxMemory() - usedMemory;

Visualizing Memory Allocation

Here is a diagram illustrating the relationship between these memory values:

[Diagram: https://i.sstatic.net/GjuwM.png]

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