# Interface ReferenceType

All Superinterfaces:
  `Accessible, Comparable<ReferenceType>, Mirror, Type`

All Known Subinterfaces:
  `ArrayType, ClassType, InterfaceType`

public interface ReferenceType extends Type, Comparable<ReferenceType>, Accessible
The type of an object in a target VM. ReferenceType encompasses classes, interfaces, and array types as defined in The Java Language Specification. All ReferenceType objects belong to one of the following subinterfaces: `ClassType` for classes, `InterfaceType` for interfaces, and `ArrayType` for arrays. Note that primitive classes (for example, the `reflected type` of `Integer.TYPE`) are represented as ClassType. The VM creates Class objects for all three, so from the VM perspective, each ReferenceType maps to a distinct Class object.

ReferenceTypes can be obtained by querying a particular `ObjectReference` for its type or by getting a list of all reference types from the `VirtualMachine`.

ReferenceType provides access to static type information such as methods and fields and provides access to dynamic type information such as the corresponding Class object and the classloader.

Any method on `ReferenceType` which directly or indirectly takes `ReferenceType` as an parameter may throw `VMDisconnectedException` if the target VM is disconnected and the `VMDisconnectEvent` has been or is available to be read from the `EventQueue`.

Any method on `ReferenceType` which directly or indirectly takes `ReferenceType` as an parameter may throw `VMOutOfMemoryException` if the target VM has run out of memory.

Any method on `ReferenceType` or which directly or indirectly takes `ReferenceType` as parameter may throw `ObjectCollectedException` if the mirrored type has been unloaded.

Since:
  1.3
See Also:
  - `ObjectReference`
  - `ObjectReference.referenceType()`
  - `VirtualMachine`
  - `VirtualMachine.allClasses()`

## Method Summary

Modifier and Type
Method
Description
`List<Field>`
`allFields()`
Returns a list containing each `Field` declared in this type, and its superclasses, implemented interfaces, and/or superinterfaces.
`List<Location>`
`allLineLocations()`
Returns a list containing a `Location` object for each executable source line in this reference type.
`List<Location>`
`allLineLocations(String stratum, String sourceName)`
Returns a list containing a `Location` object for each executable source line in this reference type.
`List<Method>`
`allMethods()`
Returns a list containing each `Method` declared in this type, and its superclasses, implemented interfaces, and/or superinterfaces.
`List<String>`
`availableStrata()`
Return the available strata for this reference type.
`ClassLoaderReference`
`classLoader()`
Gets the classloader object which loaded the class corresponding to this type.
`ClassObjectReference`
`classObject()`
Returns the class object that corresponds to this type in the target VM.
`byte[]`
`constantPool()`
Returns the raw bytes of the constant pool in the format of the constant_pool item of the Class File Format in the Java Virtual Machine Specification.
`int`
`constantPoolCount()`
Returns the number of entries in the constant pool plus one.
`String`
`defaultStratum()`
Returns the default stratum for this reference type.
`boolean`
`equals(Object obj)`
Compares the specified Object with this ReferenceType for equality.
`boolean`
`failedToInitialize()`
Determines if initialization failed for this class.
`Field`
`fieldByName(String fieldName)`
Finds the visible `Field` with the given non-ambiguous name.
`List<Field>`
`fields()`
Returns a list containing each `Field` declared in this type.
`String`
`genericSignature()`
Gets the generic signature for this type if there is one.
`Value`
`getValue(Field field)`
Gets the `Value` of a given static `Field` in this type.
`Map<Field,Value>`
`getValues(List<? extends Field> fields)`
Returns a map containing the `Value` of each static `Field` in the given list.
`int`
`hashCode()`
Returns the hash code value for this ObjectReference.
`List<ObjectReference>`
`instances(long maxInstances)`
Returns instances of this ReferenceType.
`boolean`
`isAbstract()`
Determines if this type was declared abstract.
`boolean`
`isFinal()`
Determines if this type was declared final.
`boolean`
`isInitialized()`
Determines if this type has been initialized.
`boolean`
`isPrepared()`
Determines if this type has been prepared.
`boolean`
`isStatic()`
Determines if this type was declared static.
`boolean`
`isVerified()`
Determines if this type has been verified.
`List<Location>`
`locationsOfLine(int lineNumber)`
Returns a List containing all `Location` objects that map to the given line number.
`List<Location>`
`locationsOfLine(String stratum, String sourceName, int lineNumber)`
Returns a List containing all `Location` objects that map to the given line number.
`int`
`majorVersion()`
Returns the class major version number, as defined in the class file format of the Java Virtual Machine Specification.
`List<Method>`
`methods()`
Returns a list containing each `Method` declared directly in this type.
`List<Method>`
`methodsByName(String name)`
Returns a List containing each visible `Method` that has the given name.
`List<Method>`
`methodsByName(String name, String signature)`
Returns a List containing each visible `Method` that has the given name and signature.
`int`
`minorVersion()`
Returns the class minor version number, as defined in the class file format of the Java Virtual Machine Specification.
`default ModuleReference`
`module()`
Gets the module object which contains the class corresponding to this type.
`String`
`name()`
Returns the name of this `ReferenceType` object.
`List<ReferenceType>`
`nestedTypes()`
Returns a List containing `ReferenceType` objects that are declared within this type and are currently loaded into the Virtual Machine.
`String`
`sourceDebugExtension()`
Get the source debug extension of this type.
`String`
`sourceName()`
Gets an identifying name for the source corresponding to the declaration of this type.
`List<String>`
`sourceNames(String stratum)`
Gets the identifying names for all the source corresponding to the declaration of this type.
`List<String>`
`sourcePaths(String stratum)`
Gets the paths to the source corresponding to the declaration of this type.
`List<Field>`
`visibleFields()`
Returns a list containing each unhidden and unambiguous `Field` in this type.
`List<Method>`
`visibleMethods()`
Returns a list containing each `Method` declared or inherited by this type.

### Methods declared in interface Accessible

`isPackagePrivate, isPrivate, isProtected, isPublic, modifiers`

### Methods declared in interface Comparable

`compareTo`

### Methods declared in interface Mirror

`toString, virtualMachine`

### Methods declared in interface Type

`signature`

## Method Details

### name

String name()
Returns the name of this `ReferenceType` object. The returned name is of the same form as the name returned by `Class.getName()`.

Specified by:
  `name` in interface `Type`
Returns:
  a string containing the type name.
See Also:
  - `Class.getName()`

### genericSignature

String genericSignature()
Gets the generic signature for this type if there is one. Generic signatures are described in the The Java Virtual Machine Specification.

Returns:
  a string containing the generic signature, or `null` if there is no generic signature.
Since:
  1.5

### classLoader

ClassLoaderReference classLoader()
Gets the classloader object which loaded the class corresponding to this type.

Returns:
  a `ClassLoaderReference` which mirrors the classloader, or `null` if the class was loaded through the bootstrap class loader.

### module

default ModuleReference module()
Gets the module object which contains the class corresponding to this type. Not all target virtual machines support this operation. Use `VirtualMachine.canGetModuleInfo()` to determine if the operation is supported.

Implementation Requirements:
  The default implementation throws `UnsupportedOperationException`.
Returns:
  a `ModuleReference` which mirrors the module in the target VM.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation.
Since:
  9

### sourceName

String sourceName() throws AbsentInformationException
Gets an identifying name for the source corresponding to the declaration of this type. Interpretation of this string is the responsibility of the source repository mechanism.

The returned name is dependent on VM's default stratum (`VirtualMachine.getDefaultStratum()`). In the reference implementation, when using the base stratum, the returned string is the unqualified name of the source file containing the declaration of this type. In other strata the returned source name is the first source name for that stratum. Since other languages may have more than one source name for a reference type, the use of `Location.sourceName()` or `sourceNames(String)` is preferred.

For arrays (`ArrayType`) and primitive classes, AbsentInformationException is always thrown.

Returns:
  the string source file name
Throws:
  `AbsentInformationException` - if the source name is not known

### sourceNames

List<String> sourceNames(String stratum) throws AbsentInformationException
Gets the identifying names for all the source corresponding to the declaration of this type. Interpretation of these names is the responsibility of the source repository mechanism.

The returned names are for the specified stratum (see `Location` for a description of strata). In the reference implementation, when using the Java programming language stratum, the returned List contains one element: a String which is the unqualified name of the source file containing the declaration of this type. In other strata the returned source names are all the source names defined for that stratum.

Parameters:
  `stratum` - The stratum to retrieve information from or `null` for the declaring type's default stratum.
Returns:
  a List of String objects each representing a source name
Throws:
  `AbsentInformationException` - if the source names are not known.

  For arrays (`ArrayType`) and primitive classes, AbsentInformationException is always thrown.

Since:
  1.4

### sourcePaths

List<String> sourcePaths(String stratum) throws AbsentInformationException
Gets the paths to the source corresponding to the declaration of this type. Interpretation of these paths is the responsibility of the source repository mechanism.

The returned paths are for the specified stratum (see `Location` for a description of strata). In the reference implementation, for strata which do not explicitly specify source path (the Java programming language stratum never does), the returned strings are the `sourceNames(String)` prefixed by the package name of this ReferenceType converted to a platform dependent path. For example, on a Windows platform, `java.lang.Thread` would return a List containing one element: `"java\lang\Thread.java"`.

Parameters:
  `stratum` - The stratum to retrieve information from or `null` for the declaring type's default stratum.
Returns:
  a List of String objects each representing a source path
Throws:
  `AbsentInformationException` - if the source names are not known.

  For arrays (`ArrayType`) and primitive classes, AbsentInformationException is always thrown.

Since:
  1.4

### sourceDebugExtension

String sourceDebugExtension() throws AbsentInformationException
Get the source debug extension of this type.

Not all target virtual machines support this operation. Use `canGetSourceDebugExtension()` to determine if the operation is supported.

Returns:
  as a string the source debug extension attribute
Throws:
  `AbsentInformationException` - if the extension is not specified
  `UnsupportedOperationException` - if the target virtual machine does not support this operation - see `canGetSourceDebugExtension()`,

### isStatic

boolean isStatic()
Determines if this type was declared static. Only nested types, can be declared static, so `false` is returned for any package-level type, array type, or primitive class.

Returns:
  `true` if this type is static; false otherwise.

### isAbstract

boolean isAbstract()
Determines if this type was declared abstract.

For arrays (`ArrayType`) and primitive classes, the return value is undefined.

Returns:
  `true` if this type is abstract; false otherwise.

### isFinal

boolean isFinal()
Determines if this type was declared final.

For arrays (`ArrayType`) and primitive classes, the return value is always true.

Returns:
  `true` if this type is final; false otherwise.

### isPrepared

boolean isPrepared()
Determines if this type has been prepared. See the JVM specification for a definition of class preparation.

For arrays (`ArrayType`) and primitive classes, the return value is undefined.

Returns:
  `true` if this type is prepared; false otherwise.

### isVerified

boolean isVerified()
Determines if this type has been verified. See the JVM specification for a definition of class verification.

For arrays (`ArrayType`) and primitive classes, the return value is undefined.

Returns:
  `true` if this type is verified; false otherwise.

### isInitialized

boolean isInitialized()
Determines if this type has been initialized. See the JVM specification for a definition of class verification. For `InterfaceType`, this method always returns the same value as `isPrepared()`.

For arrays (`ArrayType`) and primitive classes, the return value is undefined.

Returns:
  `true` if this type is initialized; false otherwise.

### failedToInitialize

boolean failedToInitialize()
Determines if initialization failed for this class. See the JVM specification for details on class initialization.

For arrays (`ArrayType`) and primitive classes, the return value is undefined.

Returns:
  `true` if initialization was attempted and failed; false otherwise.

### fields

List<Field> fields()
Returns a list containing each `Field` declared in this type. Inherited fields are not included. Any synthetic fields created by the compiler are included in the list.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty.

Returns:
  a list `Field` objects; the list has length 0 if no fields exist.
Throws:
  `ClassNotPreparedException` - if this class not yet been prepared.

### visibleFields

List<Field> visibleFields()
Returns a list containing each unhidden and unambiguous `Field` in this type. Each field that can be accessed from the class or its instances with its simple name is included. Fields that are ambiguously multiply inherited or fields that are hidden by fields with the same name in a more recently inherited class cannot be accessed by their simple names and are not included in the returned list. All other inherited fields are included. See JLS section 8.3 for details.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty.

Returns:
  a List of `Field` objects; the list has length 0 if no visible fields exist.
Throws:
  `ClassNotPreparedException` - if this class not yet been prepared.

### allFields

List<Field> allFields()
Returns a list containing each `Field` declared in this type, and its superclasses, implemented interfaces, and/or superinterfaces. All declared and inherited fields are included, regardless of whether they are hidden or multiply inherited.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty.

Returns:
  a List of `Field` objects; the list has length 0 if no fields exist.
Throws:
  `ClassNotPreparedException` - if this class not yet been prepared.

### fieldByName

Field fieldByName(String fieldName)
Finds the visible `Field` with the given non-ambiguous name. This method follows the inheritance rules specified in the JLS (8.3.3) to determine visibility.

For arrays (`ArrayType`) and primitive classes, the returned value is always null.

Parameters:
  `fieldName` - a String containing the name of desired field.
Returns:
  a `Field` object which mirrors the found field, or null if there is no field with the given name or if the given name is ambiguous.
Throws:
  `ClassNotPreparedException` - if this class not yet been prepared.

### methods

List<Method> methods()
Returns a list containing each `Method` declared directly in this type. Inherited methods are not included. Constructors, the initialization method if any, and any synthetic methods created by the compiler are included in the list.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty.

Returns:
  a list `Method` objects; the list has length 0 if no methods exist.
Throws:
  `ClassNotPreparedException` - if this class not yet been prepared.

### visibleMethods

List<Method> visibleMethods()
Returns a list containing each `Method` declared or inherited by this type. Methods from superclasses or superinterfaces that have been hidden or overridden are not included.

Note that despite this exclusion, multiple inherited methods with the same signature can be present in the returned list, but at most one can be a member of a `ClassType`. See JLS section 8.4.8 for details.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty.

Returns:
  a List of `Method` objects; the list has length 0 if no visible methods exist.
Throws:
  `ClassNotPreparedException` - if this class not yet been prepared.

### allMethods

List<Method> allMethods()
Returns a list containing each `Method` declared in this type, and its superclasses, implemented interfaces, and/or superinterfaces. All declared and inherited methods are included, regardless of whether they are hidden or overridden.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty.

Returns:
  a List of `Method` objects; the list has length 0 if no methods exist.
Throws:
  `ClassNotPreparedException` - if this class not yet been prepared.

### methodsByName

List<Method> methodsByName(String name)
Returns a List containing each visible `Method` that has the given name. This is most commonly used to find overloaded methods.

Overridden and hidden methods are not included. See JLS (8.4.8) for details.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty.

Parameters:
  `name` - the name of the method to find.
Returns:
  a List of `Method` objects that match the given name; the list has length 0 if no matching methods are found.
Throws:
  `ClassNotPreparedException` - if this class not yet been prepared.

### methodsByName

List<Method> methodsByName(String name, String signature)
Returns a List containing each visible `Method` that has the given name and signature. The signature string is the JNI signature for the target method:

- `()V`
- `([Ljava/lang/String;)V`
- `(IIII)Z`

This method follows the inheritance rules specified in the JLS (8.4.8) to determine visibility.

At most one method in the list is a concrete method and a component of `ClassType`; any other methods in the list are abstract. Use `ClassType.concreteMethodByName(String, String)` to retrieve only the matching concrete method.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty.

Parameters:
  `name` - the name of the method to find.
  `signature` - the signature of the method to find
Returns:
  a List of `Method` objects that match the given name and signature; the list has length 0 if no matching methods are found.
Throws:
  `ClassNotPreparedException` - if this class not yet been prepared.

### nestedTypes

List<ReferenceType> nestedTypes()
Returns a List containing `ReferenceType` objects that are declared within this type and are currently loaded into the Virtual Machine. Both static nested types and non-static nested types (that is, inner types) are included. Local inner types (declared within a code block somewhere in this reference type) are also included in the returned list.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty.

Returns:
  a List of nested `ReferenceType` objects; the list has 0 length if there are no nested types.

### getValue

Value getValue(Field field)
Gets the `Value` of a given static `Field` in this type. The Field must be valid for this type; that is, it must be declared in this type, a superclass, a superinterface, or an implemented interface.

Parameters:
  `field` - the field containing the requested value
Returns:
  the `Value` of the instance field.
Throws:
  `IllegalArgumentException` - if the field is not valid for this object's class.

### getValues

Map<Field,Value> getValues(List<? extends Field> fields)
Returns a map containing the `Value` of each static `Field` in the given list. The Fields must be valid for this type; that is, they must be declared in this type, a superclass, a superinterface, or an implemented interface.

Parameters:
  `fields` - a list of `Field` objects containing the requested values.
Returns:
  a Map of the requested `Field` objects with their `Value`.
Throws:
  `IllegalArgumentException` - if any field is not valid for this object's class.
  `VMMismatchException` - if a `Mirror` argument and this mirror do not belong to the same `VirtualMachine`.

### classObject

ClassObjectReference classObject()
Returns the class object that corresponds to this type in the target VM. The VM creates class objects for every kind of ReferenceType: classes, interfaces, and array types.

Returns:
  the `ClassObjectReference` for this reference type in the target VM.

### allLineLocations

List<Location> allLineLocations() throws AbsentInformationException
Returns a list containing a `Location` object for each executable source line in this reference type.

This method is equivalent to `allLineLocations(vm.getDefaultStratum(),null)` - see `allLineLocations(String,String)` for more information.

Throws:
  `AbsentInformationException` - if there is no line number information for this class and there are non-native, non-abstract executable members of this class.
  `ClassNotPreparedException` - if this class not yet been prepared.

### allLineLocations

List<Location> allLineLocations(String stratum, String sourceName) throws AbsentInformationException
Returns a list containing a `Location` object for each executable source line in this reference type. Each location maps a source line to a range of code indices. The beginning of the range can be determined through `Location.codeIndex()`. The returned list may contain multiple locations for a particular line number, if the compiler and/or VM has mapped that line to two or more disjoint code index ranges. Note that it is possible for the same source line to represent different code index ranges in different methods.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty. For interfaces (`InterfaceType`), the returned list will be non-empty only if the interface has executable code in its class initialization.

Returned list is for the specified stratum (see `Location` for a description of strata).

Parameters:
  `stratum` - The stratum to retrieve information from or `null` for the `defaultStratum()`.
  `sourceName` - Return locations only within this source file or `null` to return locations.
Returns:
  a List of all source line `Location` objects.
Throws:
  `AbsentInformationException` - if there is no line number information for this class and there are non-native, non-abstract executable members of this class. Or if sourceName is non-`null` and source name information is not present.
  `ClassNotPreparedException` - if this class not yet been prepared.
Since:
  1.4

### locationsOfLine

List<Location> locationsOfLine(int lineNumber) throws AbsentInformationException
Returns a List containing all `Location` objects that map to the given line number.

This method is equivalent to `locationsOfLine(vm.getDefaultStratum(), null, lineNumber)` - see `locationsOfLine(java.lang.String,java.lang.String,int)` for more information.

Parameters:
  `lineNumber` - the line number
Returns:
  a List of all `Location` objects that map to the given line.
Throws:
  `AbsentInformationException` - if there is no line number information for this class.
  `ClassNotPreparedException` - if this class not yet been prepared.
See Also:
  - `VirtualMachine.getDefaultStratum()`

### locationsOfLine

List<Location> locationsOfLine(String stratum, String sourceName, int lineNumber) throws AbsentInformationException
Returns a List containing all `Location` objects that map to the given line number.

For arrays (`ArrayType`) and primitive classes, the returned list is always empty. For interfaces (`InterfaceType`), the returned list will be non-empty only if the interface has executable code in its class initialization at the specified line number. An empty list will be returned if there is no executable code at the specified line number.

Returned list is for the specified stratum (see `Location` for a description of strata).

Parameters:
  `stratum` - the stratum to use for comparing line number and source name, or `null` to use the `defaultStratum()`.
  `sourceName` - the source name containing the line number, or `null` to match all source names
  `lineNumber` - the line number
Returns:
  a List of all `Location` objects that map to the given line.
Throws:
  `AbsentInformationException` - if there is no line number information for this class. Or if sourceName is non-`null` and source name information is not present.
  `ClassNotPreparedException` - if this class not yet been prepared.
Since:
  1.4

### availableStrata

List<String> availableStrata()
Return the available strata for this reference type.

See the `Location` for a description of strata.

Returns:
  List of `java.lang.String`, each representing a stratum
Since:
  1.4

### defaultStratum

String defaultStratum()
Returns the default stratum for this reference type. This value is specified in the class file and cannot be set by the user. If the class file does not specify a default stratum the base stratum (`"Java"`) will be returned.

See the `Location` for a description of strata.

Since:
  1.4

### instances

List<ObjectReference> instances(long maxInstances)
Returns instances of this ReferenceType. Only instances that are reachable for the purposes of garbage collection are returned.

Not all target virtual machines support this operation. Use `VirtualMachine.canGetInstanceInfo()` to determine if the operation is supported.

Parameters:
  `maxInstances` - the maximum number of instances to return. Must be non-negative. If zero, all instances are returned.
Returns:
  a List of `ObjectReference` objects. If there are no instances of this ReferenceType, a zero-length list is returned.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation - see `canGetInstanceInfo()`
  `IllegalArgumentException` - if maxInstances is less than zero.
Since:
  1.6
See Also:
  - `VirtualMachine.instanceCounts(List)`
  - `ObjectReference.referringObjects(long)`

### equals

boolean equals(Object obj)
Compares the specified Object with this ReferenceType for equality.

Overrides:
  `equals` in class `Object`
Parameters:
  `obj` - the reference object with which to compare.
Returns:
  true if the Object is a `ReferenceType`, if the ReferenceTypes belong to the same VM, and if they mirror classes which correspond to the same instance of java.lang.Class in that VM.
See Also:
  - `Object.hashCode()`
  - `HashMap`

### hashCode

int hashCode()
Returns the hash code value for this ObjectReference.

Overrides:
  `hashCode` in class `Object`
Returns:
  the integer hash code
See Also:
  - `Object.equals(java.lang.Object)`
  - `System.identityHashCode(Object)`

### majorVersion

int majorVersion()
Returns the class major version number, as defined in the class file format of the Java Virtual Machine Specification. For arrays (`ArrayType`) and primitive classes, the returned major version number value is zero. Not all target virtual machines support this operation. Use `VirtualMachine.canGetClassFileVersion()` to determine if the operation is supported.

Returns:
  the major version number of the class.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation - see `canGetClassFileVersion()`
Since:
  1.6

### minorVersion

int minorVersion()
Returns the class minor version number, as defined in the class file format of the Java Virtual Machine Specification. For arrays (`ArrayType`) and primitive classes, the returned minor version number value is zero. Not all target virtual machines support this operation. Use `VirtualMachine.canGetClassFileVersion()` to determine if the operation is supported.

Returns:
  the minor version number of the class.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation - see `canGetClassFileVersion()`
Since:
  1.6

### constantPoolCount

int constantPoolCount()
Returns the number of entries in the constant pool plus one. This corresponds to the constant_pool_count item of the Class File Format in the Java Virtual Machine Specification. For arrays (`ArrayType`) and primitive classes, the returned constant pool count value is zero. Not all target virtual machines support this operation. Use `VirtualMachine.canGetConstantPool()` to determine if the operation is supported.

Returns:
  total number of constant pool entries for a class plus one.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation - see `canGetConstantPool()`
Since:
  1.6
See Also:
  - `constantPool()`

### constantPool

byte[] constantPool()
Returns the raw bytes of the constant pool in the format of the constant_pool item of the Class File Format in the Java Virtual Machine Specification. The format of the constant pool may differ between versions of the Class File Format, so, the minor and major class version numbers should be checked for compatibility. For arrays (`ArrayType`) and primitive classes, a zero length byte array is returned. Not all target virtual machines support this operation. Use `VirtualMachine.canGetConstantPool()` to determine if the operation is supported.

Returns:
  the raw bytes of constant pool.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation - see `canGetConstantPool()`
Since:
  1.6
See Also:
  - `constantPoolCount()`