Module openj9.dtfj

Package com.ibm.dtfj.java

Interface JavaObject

All Known Implementing Classes:

CorruptJavaObject, DTFJJavaObject, JavaObject, JCJavaObject, PHDJavaObject

public interface JavaObject

Represents a Java Object.

Method Summary

Modifier and Type	Method	Description
void	arraycopy(int srcStart, Object dst, int dstStart, int length)	Copies data from the image array into a local Java array.
boolean	equals(Object obj)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
int	getArraySize()	Get the number of elements in this array.
long	getHashcode()	Fetch the basic hash code for the object.
JavaHeap	getHeap()	Gets the heap where this object is located.
ImagePointer	getID()	The ID of an object is a unique address is memory which identifies the object.
JavaClass	getJavaClass()	Get the JavaClass instance which represents the class of this object.
long	getPersistentHashcode()	Fetch the basic hash code of the object in the image.
Iterator	getReferences()	Get the set of references from this object.
Iterator	getSections()	An object is represented in the Java runtime by one or more regions of memory.
long	getSize()	Get the number of bytes of memory occupied by this object on the heap.
int	hashCode()	Answers an integer hash code for the receiver.
boolean	isArray()	Is this object an array?

Method Details

getJavaClass

JavaClass getJavaClass()
                throws CorruptDataException

Get the JavaClass instance which represents the class of this object.

Returns:

the JavaClass instance which represents the class of this object

Throws:

CorruptDataException

isArray

boolean isArray()
         throws CorruptDataException

Is this object an array?

Returns:

true if the receiver represents an instance of an array, or false otherwise

Throws:

CorruptDataException

getArraySize

int getArraySize()
          throws CorruptDataException

Get the number of elements in this array.

Returns:

the number of elements in this array

Throws:

CorruptDataException

IllegalArgumentException - if the receiver is not an array

arraycopy

void arraycopy(int srcStart,
 Object dst,
 int dstStart,
 int length)
        throws CorruptDataException,
MemoryAccessException

Copies data from the image array into a local Java array. The dst object must be an array of the appropriate type -- a base type array for base types, or a JavaObject array for reference arrays.

Parameters:

srcStart - index in the receiver to start copying from

dst - the destination array

dstStart - index in the destination array to start copying into

length - the number of elements to be copied

Throws:

CorruptDataException

MemoryAccessException

NullPointerException - if dst is null

IllegalArgumentException - if the receiver is not an array, or if dst is not an array of the appropriate type

IndexOutOfBoundsException - if srcStart, dstStart, or length are out of bounds in either the receiver or the destination array

getSize

long getSize()
      throws CorruptDataException

Get the number of bytes of memory occupied by this object on the heap. The memory may not necessarily be contiguous.

Throws:

CorruptDataException

getHashcode

long getHashcode()
          throws DataUnavailable,
CorruptDataException

Fetch the basic hash code for the object. This is the hash code which would be returned if a Java thread had requested it. Typically the hash code is based on the address of an object, and may change if the object is moved by a garbage collection cycle.

Returns:

the basic hash code of the object in the image

Throws:

DataUnavailable - if the hash code cannot be determined

CorruptDataException

See Also:

• getPersistentHashcode()

getPersistentHashcode

long getPersistentHashcode()
                    throws DataUnavailable,
CorruptDataException

Fetch the basic hash code of the object in the image. This hash code is guaranteed to be persistent between multiple snapshots of the same Image. If the hash code cannot be determined, or if the hash code for this object could change between snapshots, an exception is thrown.

If the VM uses a 'hasBeenHashed' bit, the value of this bit can be inferred by calling getPersistentHashcode(). If the persistent hash code is not available, then the 'hasBeenHashed' bit has not been set, and the hash of the object could change if the object moves between snapshots

Returns:

the basic hash code of the object in the image

Throws:

DataUnavailable - if a hash code cannot be determined, or if the hash code could change between successive snapshots

CorruptDataException

See Also:

• getHashcode()

getID

ImagePointer getID()

The ID of an object is a unique address is memory which identifies the object. The data at this memory is implementation defined. The object may be non-contiguous. Portions of the object may appear below or above this address.

Returns:

the runtime-wide unique identifier for the object

getSections

Iterator getSections()

An object is represented in the Java runtime by one or more regions of memory. These include the object's header and the data in the object. In certain allocation strategies, an object's header and data may be allocated contiguously. In this case, this method may return an iterator for a single section. In other schemes, the header may be separate from the data or the data may be broken up into multiple regions. Additionally, this function does not guarantee that the memory used by this object is not also shared by one or more other objects. Callers should not make any assumptions about the contents of the memory.

Returns:

a collection of sections that make up this object

See Also:

• ImageSection
• CorruptData

getReferences

Iterator getReferences()

Get the set of references from this object. Corrupt references will be returned as CorruptData objects by the Iterator.

Returns:

an iterator of JavaReference and CorruptData objects

See Also:

• JavaReference
• CorruptData

getHeap

JavaHeap getHeap()
          throws CorruptDataException,
DataUnavailable

Gets the heap where this object is located.

Returns:

the JavaHeap instance representing the heap where this object is stored in memory

Throws:

CorruptDataException - if the heap information for this object is corrupt

DataUnavailable - if the heap information for this object is not available

See Also:

• JavaHeap

equals

boolean equals(Object obj)

Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison. The implementation in Object answers true only if the argument is the exact same object as the receiver (==).

Overrides:

equals in class Object

Parameters:

obj - Object the object to compare with this object.

Returns:

boolean true if the object is the same as this object false if it is different from this object.

See Also:

• Object.hashCode()

hashCode

int hashCode()

Answers an integer hash code for the receiver. Any two objects which answer true when passed to .equals must answer the same value for this method.

Overrides:

hashCode in class Object

Returns:

the receiver's hash.

See Also:

• Object.equals(java.lang.Object)