MemoryUsage (GNU Classpath 0.94-pre Documentation)

Retains information on the usage of a particular memory pool, or heap/non-heap memory as a whole. Memory usage is represented by four values (all in bytes):

Initial Level: This is the initial amount of memory allocated for the pool by the operating system. This value may be undefined.
Used Level: This is the amount of memory currently in use.
Committed Level: This is the current amount of memory allocated for the pool by the operating system. This value will always be equal to or greater than the current amount of memory in use. It may drop below the initial amount, if the virtual machine judges this to be practical.
Maximum Level: This is the maximum amount of memory that may be allocated for the pool by the operating system. Like the initial amount, it may be undefined. If it is defined, it will be greater than or equal to the used and committed amounts and may change over time. It is not guaranteed that the maximum amount of memory may actually be allocated to the pool. For example, a request for an amount of memory greater than the current committed level, but less than the maximum, may still fail due to resources at the operating system level not being sufficient to fulfill the demand.

Since: 1.5

See Also: MemoryMXBean MemoryPoolMXBean

Constructor Summary
	MemoryUsage(long init, long used, long committed, long maximum) Constructs a new {@link MemoryUsage} object with the specified allocation levels.

Method Summary
static MemoryUsage	from(CompositeData data) Returns a {@link MemoryUsage} instance using the values given in the supplied {@link javax.management.openmbean.CompositeData} object.
long	getCommitted() Returns the amount of memory committed for use by this memory pool (in bytes).
long	getInit() Returns the initial amount of memory allocated to the pool (in bytes).
long	getMax() Returns the maximum amount of memory available for this pool (in bytes).
long	getUsed() Returns the amount of memory used (in bytes).
String	toString() Returns a {@link java.lang.String} representation of this {@link MemoryUsage} object.

Constructor Detail

MemoryUsage

Constructs a new {@link MemoryUsage} object with the specified allocation levels.

Parameters: init the initial amount of memory allocated, or -1 if this value is undefined. Must be >= -1. used the amount of memory used. Must be >= 0, and <= committed. committed the amount of memory committed for use at present. Must be >= 0 and <= maximum (if defined). maximum the maximum amount of memory that may be used, or -1 if this value is undefined. Must be >= -1.

Throws: IllegalArgumentException if the values break any of the limits specified above.

Method Detail

from

Returns a {@link MemoryUsage} instance using the values given in the supplied {@link javax.management.openmbean.CompositeData} object. The composite data instance should contain the following attributes:

init
used
committed
max

All should have the type, java.lang.Long.

Parameters: data the composite data structure to take values from.

Returns: a new instance containing the values from the composite data structure, or null if the data structure was also null.

Throws: IllegalArgumentException if the composite data structure does not match the structure outlined above, or the values are invalid.

getCommitted

getInit

getMax

Returns the maximum amount of memory available for this pool (in bytes). This amount is not guaranteed to actually be usable. This method may return -1, if the value is undefined.

Returns: the maximum amount of memory available, or -1 if this value is undefined.

getUsed

toString

Returns a {@link java.lang.String} representation of this {@link MemoryUsage} object. This takes the form

java.lang.management.MemoryUsage[init=i, used=u,
 committed=c, maximum=m]

, where i is the initial level, u is the used level, c is the committed level and m is the maximum level.

Returns: the string specified above.

Class MemoryUsage