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 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.

    • isValid

      public boolean isValid()
      Whether the data returned by this GcInfo object has passed all validity tests.
      Returns:
      true if the data in this GcInfo is valid; otherwise, false.

    • getGarbageCollectionCause

      public String getGarbageCollectionCause()
      The reason for this collection. The most common one is when the Java virtual machine detects that all available Java heap space has been occupied, or that the Java virtual machine estimates that all available space will soon be occupied. A Java virtual machine might use "Max" as the string to identify this cause for starting a collection, or possibly "Alo" for an object allocation failure. The reason is unique across all collectors supported by the Java virtual machine.
      Returns:
      a String representing the reason for this collection.

    • getLiveInPoolsBeforeGc

      public long getLiveInPoolsBeforeGc()
      At the start of this collection, the approximate number of bytes occupied by live objects in the memory pools affected by the associated collector. If this operation is not supported, this method returns -1.

      Note that "the memory pools affected by the associated collector" may not be the same as "the memory pools affected by this collection".

      Returns:
      the approximate number of bytes occupied by live objects in the memory pools affected by the associated collector at the start of this collection; or -1 if this operation is not supported.

    • getLiveInPoolsAfterGc

      public long getLiveInPoolsAfterGc()
      At the end of this collection, the approximate number of bytes occupied by live objects in the memory pools affected by the associated collector. If this operation is not supported, this method returns -1.

      Note that "the memory pools affected by the associated collector" may not be the same as "the memory pools affected by this collection".

      Returns:
      the approximate number of bytes occupied by live objects in the memory pools affected by the associated collector at the end of this collection; or -1 if this operation is not supported.

    • getGarbageFound

      public long getGarbageFound()
      The aggregate size, in bytes, of all unreachable objects discovered by the associated collector during this collection.
      Returns:
      the aggregate size, in bytes, of all unreachable objects discovered by the associated collector during this collection.

    • getGarbageCollected

      public long getGarbageCollected()
      The aggregate size, in bytes, of all objects collected by the associated collector during this collection.
      Returns:
      the aggregate size, in bytes, of all objects collected by the associated collector during this collection.

    • getCopiedBetweenPools

      public long getCopiedBetweenPools()
      If objects were copied between the memory pools affected by this collection, their aggregate size in bytes. If this is a young collection in a two-generation system, this value is the total size of objects promoted to the old generation. This value is not the same as the difference in before and after MemoryUsage occupancy because allocation in the target MemoryPool(s) may have been done by other than the GC threads that ran this collection.
      Returns:
      the aggregate size in bytes of objects copied between the memory pools affected by this collection.

    • getStartTimeNanos

      public long getStartTimeNanos()
      The approximate start time of this collection in nanoseconds since Java virtual machine launch.
      Returns:
      the start time of this collection.

    • getEndTimeNanos

      public long getEndTimeNanos()
      The approximate end time of this collection in nanoseconds since Java virtual machine launch.
      Returns:
      the end time of this collection.

    • getDurationNanos

      public long getDurationNanos()
      The approximate elapsed wall clock time in nanoseconds between the start and end of this collection. The returned value is equal to getEndTimeNanos() - getStartTimeNanos().
      Returns:
      the elapsed time of this collection.

    • getTimeFromEndOfPreviousToStartNanos

      public long getTimeFromEndOfPreviousToStartNanos()
      The approximate amount of time in nanoseconds from the end of the last previous collection run by the associated collector to the start of this collection. The time interval represents the amount of time the collector did not run.
      Returns:
      the amount of time from the end of the last previous collection run by the associated collector to the start of this collection.

    • getPercentageOfTimeCollectorWasRunning

      public double getPercentageOfTimeCollectorWasRunning()
      The percentage of time that the associated collector ran over the time interval between the end of the last previous collection run by it and the end of this collection. The percentage is calculated by: ( getDurationSeconds() / ( (double)getTimeFromEndOfPreviousToStartNanos() + getDurationSeconds() ) ) * 100.
      Returns:
      the percentage of time the associated collector ran between the end of its last previous collection and the end of this collection.

    • getAllocRateDuringCollection

      public double getAllocRateDuringCollection()
      The approximate object allocation rate in megabytes per second in the memory pools affected by the associated collector during the time interval returned by getDurationNanos.

      Note that "the memory pools affected by the associated collector" may not be the same as "the memory pools affected by this collection".

      Returns:
      the object allocation rate in megabytes per second during the time interval between the start and end of this collection.

    • getAllocRateBetweenEndOfPreviousAndStart

      public double getAllocRateBetweenEndOfPreviousAndStart()
      The approximate object allocation rate in megabytes per second in the memory pools affected by the associated collector during the time interval returned by getTimeFromEndOfPreviousToStartNanos.

      Note that "the memory pools affected by the associated collector" may not be the same as "the memory pools affected by this collection".

      Returns:
      the object allocation rate in megabytes per second during the time interval between the end of the last previous collection and the start of this collection.

    • getPreviousEndTimeNanos

      public long getPreviousEndTimeNanos()
      The approximate end time of the last previous collection in nanoseconds since Java virtual machine launch.
      Returns:
      the end time of the last previous collection.

    • getAllocatedDuringCollection

      public long getAllocatedDuringCollection()
      The number of bytes allocated in the memory pools affected by the associated collector during the time interval returned by getDurationNanos.

      Note that "the memory pools affected by the associated collector" may not be the same as "the memory pools affected by this collection".

      Returns:
      the object allocated bytes during the time interval between the start and end of this collection.

    • getAllocatedBetweenEndOfPreviousAndStart

      public long getAllocatedBetweenEndOfPreviousAndStart()
      The number of bytes allocated in the memory pools affected by the associated collector during the time interval returned by getTimeFromEndOfPreviousToStartNanos.

      Note that "the memory pools affected by the associated collector" may not be the same as "the memory pools affected by this collection".

      Returns:
      the object allocated bytes during the time interval between the end of the last previous collection and the start of this collection.

    • getPauseInfo

      public List<PauseInfo> getPauseInfo()
      A List of PauseInfo for the pauses required during this collection.
      Returns:
      a List of PauseInfo for the pauses during this collection.

    • getConcurrentInfo

      public List<ConcurrentInfo> getConcurrentInfo()
      A List of ConcurrentInfo for the concurrent phases of this collection.
      Returns:
      a List of ConcurrentInfo for the concurrent phases of this collection.

    • getVersion

      public long getVersion()
      The version of this GcInfo that determines the attributes it supports.
      Returns:
      a Long representing the GcInfo version.

    • 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 class: 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.

      An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes.

      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:

    • 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 class: 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 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 equals 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.
      Specified by:
      hashCode in interface CompositeData
      Overrides:
      hashCode in class Object
      Returns:
      a hash code value for this object.
      See Also:

    • toString

      public String toString()
      Description copied from class: Object
      Returns a string representation of the object.
      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: 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.