Module jdk.management
Package com.sun.management

Class 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 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:
        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.

        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: 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.

      • 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(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. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.)

        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: 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: 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.