public class MemoryUsage extends Object
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:
Value | Description |
---|---|
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). |
+----------------------------------------------+ +//////////////// | + +//////////////// | + +----------------------------------------------+ |--------| init |---------------| used |---------------------------| committed |----------------------------------------------| max
MemoryUsage
is mapped to a CompositeData
with attributes as specified in the from
method.Constructor | Description |
---|---|
MemoryUsage |
Constructs a MemoryUsage object. |
Modifier and Type | Method | Description |
---|---|---|
static MemoryUsage |
from |
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. |
public MemoryUsage(long init, long used, long committed, long max)
MemoryUsage
object.init
- the initial amount of memory in bytes that the Java virtual machine allocates; or -1
if undefined.used
- the amount of used memory in bytes.committed
- the amount of committed memory in bytes.max
- the maximum amount of memory in bytes that can be used; or -1
if undefined.IllegalArgumentException
- if init
or max
is negative but not -1
; orused
or committed
is negative; orused
is greater than the value of committed
; orcommitted
is greater than the value of max
max
if defined.public long getInit()
-1
if the initial memory size is undefined.-1
if undefined.public long getUsed()
public long getCommitted()
public long getMax()
-1
if the maximum memory size is undefined. This amount of memory is not guaranteed to be available for memory management if it is greater than the amount of committed memory. The Java virtual machine may fail to allocate memory even if the amount of used memory does not exceed this maximum size.
-1
if undefined.public String toString()
public static MemoryUsage from(CompositeData cd)
MemoryUsage
object represented by the given CompositeData
. The given CompositeData
must contain the following attributes: Attribute Name | Type |
---|---|
init | java.lang.Long |
used | java.lang.Long |
committed | java.lang.Long |
max | java.lang.Long |
cd
- CompositeData
representing a MemoryUsage
MemoryUsage
object represented by cd
if cd
is not null
; null
otherwise.IllegalArgumentException
- if cd
does not represent a MemoryUsage
with the attributes described above.
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.management/java/lang/management/MemoryUsage.html