MemoryUsage (Java Platform SE 8 ) (original) (raw)

java.lang.Object
- java.lang.management.MemoryUsage

public class MemoryUsage
extends Object
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.
Since:
1.5

Constructor Summary

Constructors

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

Method Summary

All Methods Static Methods Instance Methods Concrete Methods

Modifier and Type	Method	Description
static MemoryUsage	from(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](../../../java/lang/Object.html "class in java.lang")  
   `[clone](../../../java/lang/Object.html#clone--), [equals](../../../java/lang/Object.html#equals-java.lang.Object-), [finalize](../../../java/lang/Object.html#finalize--), [getClass](../../../java/lang/Object.html#getClass--), [hashCode](../../../java/lang/Object.html#hashCode--), [notify](../../../java/lang/Object.html#notify--), [notifyAll](../../../java/lang/Object.html#notifyAll--), [wait](../../../java/lang/Object.html#wait--), [wait](../../../java/lang/Object.html#wait-long-), [wait](../../../java/lang/Object.html#wait-long-int-)`

Constructor Detail

 * #### MemoryUsage  
 public MemoryUsage(long init,  
                    long used,  
                    long committed,  
                    long max)  
 Constructs a  
 MemoryUsage  
  object.  
 Parameters:  
 `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.  
 Throws:  
 `[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if  
          * the value of init or max is negative but not \-1; or  
          * the value of used or committed is negative; or  
          * used is greater than the value of committed; or  
          * committed is greater than the value of max max if defined.

Method Detail

* #### getInit  
public long getInit()  
Returns the amount of memory in bytes that the Java virtual machine initially requests from the operating system for memory management. This method returns  
\-1  
 if the initial memory size is undefined.  
Returns:  
the initial size of memory in bytes;\-1 if undefined.  
* #### getUsed  
public long getUsed()  
Returns the amount of used memory in bytes.  
Returns:  
the amount of used memory in bytes.  
* #### getCommitted  
public long getCommitted()  
Returns the amount of memory in bytes that is committed for the Java virtual machine to use. This amount of memory is guaranteed for the Java virtual machine to use.  
Returns:  
the amount of committed memory in bytes.  
* #### getMax  
public long getMax()  
Returns the maximum amount of memory in bytes that can be used for memory management. This method returns  
\-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.  
Returns:  
the maximum amount of memory in bytes;\-1 if undefined.  
* #### toString  
public [String](../../../java/lang/String.html "class in java.lang") toString()  
Returns a descriptive representation of this memory usage.  
Overrides:  
`[toString](../../../java/lang/Object.html#toString--)` in class `[Object](../../../java/lang/Object.html "class in java.lang")`  
Returns:  
a string representation of the object.  
* #### from  
public static [MemoryUsage](../../../java/lang/management/MemoryUsage.html "class in java.lang.management") from([CompositeData](../../../javax/management/openmbean/CompositeData.html "interface in javax.management.openmbean") cd)  
Returns a  
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 |  
Parameters:  
`cd` \- CompositeData representing a MemoryUsage  
Returns:  
a MemoryUsage object represented by cd if cd is not null;null otherwise.  
Throws:  
`[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if cd does not represent a MemoryUsage with the attributes described above.

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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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MemoryUsage (Java Platform SE 8 ) (original) (raw)

MXBean Mapping

Constructor Summary

Method Summary

Constructor Detail

Method Detail