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I am creating a scheduled executor to read the memory usage of the JVM. I have come across two ways to get memory statistics in a running JVM - Runtime & MemoryMXBean, with the following correspondence between their methods:

memoryMxBean.getHeapMemoryUsage().getUsed()      <=> runtime.totalMemory() - runtime.freeMemory()
memoryMxBean.getHeapMemoryUsage().getCommitted() <=> runtime.totalMemory()
memoryMxBean.getHeapMemoryUsage().getMax()       <=> runtime.maxMemory()

With the exception of the additional non-heap memory usage information provided by MemoryMXBean, are there any reasons why I should prefer it over Runtime, or vice-versa?

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7

There are none. JMX bean can be accessed externally and is meant for management tools like hyperic ( or even nagios ) - It would delegate to Runtime anyway.

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Yes. Both ways return exactly the same value for the used memory.
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If you're trying to opt for performance: Runtime.getRuntime().totalMemory()/freeMemory()/maxMemory() are inlined native calls, whereas MemoryMXBean.getHeapMemoryUsage() involves more indirection and object allocation.

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