Module openj9.dtfj

Package com.ibm.dtfj.java.j9

Class JavaArrayClass

java.lang.Object

com.ibm.dtfj.java.j9.JavaAbstractClass

com.ibm.dtfj.java.j9.JavaArrayClass

All Implemented Interfaces:

JavaClass

public class JavaArrayClass
extends JavaAbstractClass

Field Summary

Fields declared in class com.ibm.dtfj.java.j9.JavaAbstractClass

_classPointer, _javaVM

Fields declared in interface com.ibm.dtfj.java.JavaClass

MODIFIERS_UNAVAILABLE

Constructor Summary

Constructors

Constructor	Description
JavaArrayClass(JavaRuntime runtime, ImagePointer pointer, int modifiers, int flagOffset, int sizeOffset, int bytesForSize, int firstElementOffset, long leafClassID, int dimension, long loaderID, ImagePointer objectID, int hashcodeSlot)

Method Summary

Modifier and Type	Method	Description
int	getBytesPerElement(int refFieldSize)	Looks up the class name of the child elements to determine the size of one element
JavaClass	getComponentType()	For array classes, returns a JavaClass representing the component type of this array class.
Iterator	getConstantPoolReferences()	Java classes may refer to other classes and to String objects via the class's constant pool.
Iterator	getDeclaredFields()	Get the set of fields declared in this class.
Iterator	getDeclaredMethods()	Get the set of methods declared in this class.
int	getFirstElementOffset()
long	getInstanceSize()	Returns the size in bytes of an instance of this class on the heap.
int	getInstanceSize(JavaObject instance)
JavaClass	getLeafClass()
String	getName()	Get the name of the class.
int	getNumberOfSizeBytes()
Iterator	getReferences()	Get the set of references from this class.
int	getSizeOffset()
JavaClass	getSuperclass()	Get the immediate superclass of this class.
boolean	isArray()	Is this an array class ?

Methods declared in class com.ibm.dtfj.java.j9.JavaAbstractClass

addClassLoaderReference, addClassObjectReference, addInterfaceName, addSuperclassReference, equals, getClassLoader, getHashcodeSlotSize, getID, getInterfaces, getModifiers, getObject, getProtectionDomain, hashCode, readFlagsFromInstance

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

JavaArrayClass

public JavaArrayClass(JavaRuntime runtime,
 ImagePointer pointer,
 int modifiers,
 int flagOffset,
 int sizeOffset,
 int bytesForSize,
 int firstElementOffset,
 long leafClassID,
 int dimension,
 long loaderID,
 ImagePointer objectID,
 int hashcodeSlot)

Method Details

getName

public String getName()
               throws CorruptDataException

Description copied from interface: JavaClass

Get the name of the class.

Returns:

the name of the class in the form: "full/package/class$innerclass"

Throws:

CorruptDataException

getSuperclass

public JavaClass getSuperclass()
                        throws CorruptDataException

Description copied from interface: JavaClass

Get the immediate superclass of this class.

Returns:

the immediate superclass of this class, or null if this class has no superclass. For interfaces, Object, primitive types and void null is always returned.

Throws:

CorruptDataException

isArray

public boolean isArray()
                throws CorruptDataException

Description copied from interface: JavaClass

Is this an array class ?

Returns:

true if this class is an array class

Throws:

CorruptDataException

getLeafClass

public JavaClass getLeafClass()

getComponentType

public JavaClass getComponentType()
                           throws CorruptDataException

Description copied from interface: JavaClass

For array classes, returns a JavaClass representing the component type of this array class.

Returns:

a JavaClass representing the component type of this array class

Throws:

CorruptDataException

getDeclaredFields

public Iterator getDeclaredFields()

Description copied from interface: JavaClass

Get the set of fields declared in this class.

Returns:

an iterator over the collection of fields declared in this class.

See Also:

• JavaField
• CorruptData

getDeclaredMethods

public Iterator getDeclaredMethods()

Description copied from interface: JavaClass

Get the set of methods declared in this class.

Returns:

an iterator over the collection of methods declared in this class.

See Also:

• JavaMethod
• CorruptData

getConstantPoolReferences

public Iterator getConstantPoolReferences()

Description copied from interface: JavaClass

Java classes may refer to other classes and to String objects via the class's constant pool. These references are followed by the garbage collector, forming edges on the graph of reachable objects. This getConstantPoolReferences() may be used to determine which objects are referred to by the receiver's constant pool.

Although Java VMs typically permit only Class and String objects in the constant pool, some esoteric or future virtual machines may permit other types of objects to occur in the constant pool. This API imposes no restrictions on the types of JavaObjects which might be included in the Iterator.

No assumption should be made about the order in which constant pool references are returned.

Classes may also refer to objects through static variables. These may be found with the getDeclaredFields() API. Objects referenced by static variables are not returned by getConstantPoolReferences() unless the object is also referenced by the constant pool.

Returns:

an iterator over the collection of JavaObjects which are referred to by the constant pool of this class

See Also:

• JavaObject
• CorruptData

getInstanceSize

public int getInstanceSize(JavaObject instance)

Specified by:

getInstanceSize in class JavaAbstractClass

Parameters:

instance - The instance is needed for array types to calculate the size of a per-instance basis

Returns:

The size, in bytes, of an instance of this class (required for iterating the heap)

getBytesPerElement

public int getBytesPerElement(int refFieldSize)
                       throws CorruptDataException

Looks up the class name of the child elements to determine the size of one element

Parameters:

refFieldSize - The size of reference fields (fj9object_t) in the heap of the object instance we are sizing

Returns:

The size of one element, in bytes

Throws:

CorruptDataException

getFirstElementOffset

public int getFirstElementOffset()

Returns:

getSizeOffset

public int getSizeOffset()

Returns:

The offset into an array where the length (in elements) is found

getNumberOfSizeBytes

public int getNumberOfSizeBytes()

Returns:

The number of bytes to read from the object header as the size field

getReferences

public Iterator getReferences()

Description copied from interface: JavaClass

Get the set of references from this class.

Returns:

an iterator of JavaReferences

See Also:

• JavaReference
• CorruptData

getInstanceSize

public long getInstanceSize()
                     throws CorruptDataException

Description copied from interface: JavaClass

Returns the size in bytes of an instance of this class on the heap.

The call is only meaningful for a non-array JavaClass, where all instances of the class are of the same size. If this method is called on a JavaArrayClass, where instances can be of different sizes, an UnsupportedOperationException will be thrown. DataUnavailable can be thrown if no value is available: for example when DTFJ is examining a javacore, where the instance size for a class is not recorded.

Returns:

size in bytes of an instance

Throws:

CorruptDataException