Module jdk.management

Package com.sun.management

Class GcInfo

java.lang.Object

com.sun.management.GcInfo

All Implemented Interfaces:

CompositeData, CompositeDataView

public class GcInfo
extends Object
implements CompositeData, CompositeDataView

Garbage collection information. It contains the following information for one garbage collection as well as GC-specific attributes:

• Start time
• End time
• Duration
• Memory usage before the collection starts
• Memory usage after the collection ends

GcInfo is a CompositeData The GC-specific attributes can be obtained via the CompositeData interface. This is a historical relic, and other classes should not copy this pattern. Use CompositeDataView instead.

MXBean Mapping

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

Since:

1.5

Method Summary

Modifier and Type	Method	Description
boolean	containsKey(String key)	Returns true if and only if this CompositeData instance contains an item whose name is key.
boolean	containsValue(Object value)	Returns true if and only if this CompositeData instance contains an item whose value is value.
boolean	equals(Object obj)	Compares the specified obj parameter with this CompositeData instance for equality.
static GcInfo	from(CompositeData cd)	Returns a GcInfo object represented by the given CompositeData.
Object	get(String key)	Returns the value of the item whose name is key.
Object[]	getAll(String[] keys)	Returns an array of the values of the items whose names are specified by keys, in the same order as keys.
CompositeType	getCompositeType()	Returns the composite type of this composite data instance.
long	getDuration()	Returns the elapsed time of this GC in milliseconds.
long	getEndTime()	Returns the end time of this GC in milliseconds since the Java virtual machine was started.
long	getId()	Returns the identifier of this garbage collection which is the number of collections that this collector has done.
Map<String,MemoryUsage>	getMemoryUsageAfterGc()	Returns the memory usage of all memory pools at the end of this GC.
Map<String,MemoryUsage>	getMemoryUsageBeforeGc()	Returns the memory usage of all memory pools at the beginning of this GC.
long	getStartTime()	Returns the start time of this GC in milliseconds since the Java virtual machine was started.
int	hashCode()	Returns the hash code value for this CompositeData instance.
CompositeData	toCompositeData(CompositeType ct)	Return the CompositeData representation of this GcInfo, including any GC-specific attributes.
String	toString()	Returns a string representation of this CompositeData instance.
Collection<?>	values()	Returns an unmodifiable Collection view of the item values contained in this CompositeData instance.

Methods declared in class java.lang.Object

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

Method Details

getId

public long getId()

Returns the identifier of this garbage collection which is the number of collections that this collector has done.

Returns:

the identifier of this garbage collection which is the number of collections that this collector has done.

getStartTime

public long getStartTime()

Returns the start time of this GC in milliseconds since the Java virtual machine was started.

Returns:

the start time of this GC.

getEndTime

public long getEndTime()

Returns the end time of this GC in milliseconds since the Java virtual machine was started.

Returns:

the end time of this GC.

getDuration

public long getDuration()

Returns the elapsed time of this GC in milliseconds.

Returns:

the elapsed time of this GC in milliseconds.

getMemoryUsageBeforeGc

public Map<String,MemoryUsage> getMemoryUsageBeforeGc()

Returns the memory usage of all memory pools at the beginning of this GC. This method returns a Map of the name of a memory pool to the memory usage of the corresponding memory pool before GC starts.

Returns:

a Map of memory pool names to the memory usage of a memory pool before GC starts.

getMemoryUsageAfterGc

public Map<String,MemoryUsage> getMemoryUsageAfterGc()

Returns the memory usage of all memory pools at the end of this GC. This method returns a Map of the name of a memory pool to the memory usage of the corresponding memory pool when GC finishes.

Returns:

a Map of memory pool names to the memory usage of a memory pool when GC finishes.

from

public static GcInfo from(CompositeData cd)

Returns a GcInfo object represented by the given CompositeData. The given CompositeData must contain all the following attributes:

description

Attribute Name	Type
index	java.lang.Long
startTime	java.lang.Long
endTime	java.lang.Long
memoryUsageBeforeGc	javax.management.openmbean.TabularData
memoryUsageAfterGc	javax.management.openmbean.TabularData

Returns:

a GcInfo object represented by cd if cd is not null; null otherwise.

Throws:

IllegalArgumentException - if cd does not represent a GcInfo object with the attributes described above.

containsKey

public boolean containsKey(String key)

Description copied from interface: CompositeData

Returns true if and only if this CompositeData instance contains an item whose name is key. If key is a null or empty String, this method simply returns false.

Specified by:

containsKey in interface CompositeData

Parameters:

key - the key to be tested.

Returns:

true if this CompositeData contains the key.

containsValue

public boolean containsValue(Object value)

Description copied from interface: CompositeData

Returns true if and only if this CompositeData instance contains an item whose value is value.

Specified by:

containsValue in interface CompositeData

Parameters:

value - the value to be tested.

Returns:

true if this CompositeData contains the value.

equals

public boolean equals(Object obj)

Description copied from interface: CompositeData

Compares the specified obj parameter with this CompositeData instance for equality.

Returns true if and only if all of the following statements are true:

• obj is non null,
• obj also implements the CompositeData interface,
• their composite types are equal
• their contents, i.e. (name, value) pairs are equal. If a value contained in the content is an array, the value comparison is done as if by calling the deepEquals method for arrays of object reference types or the appropriate overloading of Arrays.equals(e1,e2) for arrays of primitive types

This ensures that this equals method works properly for obj parameters which are different implementations of the CompositeData interface, with the restrictions mentioned in the equals method of the java.util.Collection interface.

Specified by:

equals in interface CompositeData

Overrides:

equals in class Object

Parameters:

obj - the object to be compared for equality with this CompositeData instance.

Returns:

true if the specified object is equal to this CompositeData instance.

See Also:

• Object.hashCode()
• HashMap

get

public Object get(String key)

Description copied from interface: CompositeData

Returns the value of the item whose name is key.

Specified by:

get in interface CompositeData

Parameters:

key - the name of the item.

Returns:

the value associated with this key.

getAll

public Object[] getAll(String[] keys)

Description copied from interface: CompositeData

Returns an array of the values of the items whose names are specified by keys, in the same order as keys.

Specified by:

getAll in interface CompositeData

Parameters:

keys - the names of the items.

Returns:

the values corresponding to the keys.

getCompositeType

public CompositeType getCompositeType()

Description copied from interface: CompositeData

Returns the composite type of this composite data instance.

Specified by:

getCompositeType in interface CompositeData

Returns:

the type of this CompositeData.

hashCode

public int hashCode()

Description copied from interface: CompositeData

Returns the hash code value for this CompositeData instance.

The hash code of a CompositeData instance is the sum of the hash codes of all elements of information used in equals comparisons (ie: its composite type and all the item values).

This ensures that t1.equals(t2) implies that t1.hashCode()==t2.hashCode() for any two CompositeData instances t1 and t2, as required by the general contract of the method Object.hashCode().

Each item value's hash code is added to the returned hash code. If an item value is an array, its hash code is obtained as if by calling the deepHashCode method for arrays of object reference types or the appropriate overloading of Arrays.hashCode(e) for arrays of primitive types.

Specified by:

hashCode in interface CompositeData

Overrides:

hashCode in class Object

Returns:

the hash code value for this CompositeData instance

See Also:

• Object.equals(java.lang.Object)
• System.identityHashCode(java.lang.Object)

toString

public String toString()

Description copied from interface: CompositeData

Returns a string representation of this CompositeData instance.

The string representation consists of the name of the implementing class, the string representation of the composite type of this instance, and the string representation of the contents (ie list the itemName=itemValue mappings).

Specified by:

toString in interface CompositeData

Overrides:

toString in class Object

Returns:

a string representation of this CompositeData instance

values

public Collection<?> values()

Description copied from interface: CompositeData

Returns an unmodifiable Collection view of the item values contained in this CompositeData instance. The returned collection's iterator will return the values in the ascending lexicographic order of the corresponding item names.

Specified by:

values in interface CompositeData

Returns:

the values.

toCompositeData

public CompositeData toCompositeData(CompositeType ct)

Return the CompositeData representation of this GcInfo, including any GC-specific attributes. The returned value will have at least all the attributes described in the from method, plus optionally other attributes.

Specified by:

toCompositeData in interface CompositeDataView

Parameters:

ct - the CompositeType that the caller expects. This parameter is ignored and can be null.

Returns:

the CompositeData representation.