A MemoryUsage object represents a snapshot of memory usage. Instances of the MemoryUsage class are usually constructed by methods that are used to obtain memory usage information about individual memory pool of the Java virtual machine or the heap or non-heap memory of the Java virtual machine as a whole.

A MemoryUsage object contains four values:

init	represents the initial amount of memory (in bytes) that the Java virtual machine requests from the operating system for memory management during startup. The Java virtual machine may request additional memory from the operating system and may also release memory to the system over time. The value of init may be undefined.
used	represents the amount of memory currently used (in bytes).
committed	represents the amount of memory (in bytes) that is guaranteed to be available for use by the Java virtual machine. The amount of committed memory may change over time (increase or decrease). The Java virtual machine may release memory to the system and committed could be less than init. committed will always be greater than or equal to used.
max	represents the maximum amount of memory (in bytes) that can be used for memory management. Its value may be undefined. The maximum amount of memory may change over time if defined. The amount of used and committed memory will always be less than or equal to max if max is defined. A memory allocation may fail if it attempts to increase the used memory such that used > committed even if used <= max would still be true (for example, when the system is low on virtual memory).

Below is a picture showing an example of a memory pool:

        +----------------------------------------------+
        +////////////////           |                  +
        +////////////////           |                  +
        +----------------------------------------------+

        |--------|
           init
        |---------------|
               used
        |---------------------------|
                  committed 
        |----------------------------------------------|
                            max 
 

MXBean Mapping

MemoryUsage is mapped to a CompositeData with attributes as specified in the from method.

Constructor Summary

MemoryUsage(long init, long used, long committed, long max) Constructs a MemoryUsage object.

Method Summary
static MemoryUsage	from(javax.management.openmbean.CompositeData cd) Returns a MemoryUsage object represented by the given CompositeData.
long	getCommitted() Returns the amount of memory in bytes that is committed for the Java virtual machine to use.
long	getInit() Returns the amount of memory in bytes that the Java virtual machine initially requests from the operating system for memory management.
long	getMax() Returns the maximum amount of memory in bytes that can be used for memory management.
long	getUsed() Returns the amount of used memory in bytes.
String	toString() Returns a descriptive representation of this memory usage.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait