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/OpenJDK 25

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 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:

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:

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.

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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/25/docs/api/jdk.management/com/sun/management/GcInfo.html