GcInfo (Monitoring and Management Interface for the Java Platform )

java.lang.Object
- com.sun.management.GcInfo

All Implemented Interfaces:

CompositeData, CompositeDataView
```
@Exported
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

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and 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)` Indicates whether some other object is "equal to" this one.
`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 a hash code value for the object.
`CompositeData`	`toCompositeData(CompositeType ct)` Return the `CompositeData` representation of this `GcInfo`, including any GC-specific attributes.
`String`	`toString()` Returns a string representation of the object.
`Collection`	`values()` Returns an unmodifiable Collection view of the item values contained in this `CompositeData` instance.

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

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:

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

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: javax.management.openmbean.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: javax.management.openmbean.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 class: java.lang.Object
Indicates whether some other object is "equal to" this one.
The equals method implements an equivalence relation on non-null object references:
- It is reflexive: for any non-null reference value x, x.equals(x) should return true.
- It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
- It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
- It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
- For any non-null reference value x, x.equals(null) should return false.
The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).
Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.
Specified by:

equals in interface CompositeData

Overrides:

equals in class Object

Parameters:

obj - the reference object with which to compare.

Returns:

true if this object is the same as the obj argument; false otherwise.

See Also:

Object.hashCode(), HashMap

get
```
public Object get(String key)
```
Description copied from interface: javax.management.openmbean.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: javax.management.openmbean.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: javax.management.openmbean.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 class: java.lang.Object
Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.
The general contract of hashCode is:
- Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
- If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
- It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java™ programming language.)
Specified by:

hashCode in interface CompositeData

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

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

toString
```
public String toString()
```
Description copied from class: java.lang.Object
Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.
The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:
```
 getClass().getName() + '@' + Integer.toHexString(hashCode())
 
```
Specified by:

toString in interface CompositeData

Overrides:

toString in class Object

Returns:

a string representation of the object.

values
```
public Collection values()
```
Description copied from interface: javax.management.openmbean.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.

Class GcInfo

MXBean Mapping

Method Summary

Methods inherited from class java.lang.Object

Method Detail

getId

getStartTime

getEndTime

getDuration

getMemoryUsageBeforeGc

getMemoryUsageAfterGc

from

containsKey

containsValue

equals

get

getAll

getCompositeType

hashCode

toString

values

toCompositeData