- All Implemented Interfaces:
AnnotatedElement
,Member
Field
provides information about, and dynamic access to, a
single field of a class or an interface. The reflected field may
be a class (static) field or an instance field.
A Field
permits widening conversions to occur during a get or
set access operation, but throws an IllegalArgumentException
if a
narrowing conversion would occur.
- Since:
- 1.1
- See Also:
-
Field Summary
-
Method Summary
Modifier and TypeMethodDescriptionReturns an unmodifiable set of the access flags for this field, possibly empty.boolean
Compares thisField
against the specified object.Returns the value of the field represented by thisField
, on the specified object.Returns an AnnotatedType object that represents the use of a type to specify the declared type of the field represented by this Field.<T extends Annotation>
TgetAnnotation
(Class<T> annotationClass) Returns this element's annotation for the specified type if such an annotation is present, else null.<T extends Annotation>
T[]getAnnotationsByType
(Class<T> annotationClass) Returns annotations that are associated with this element.boolean
getBoolean
(Object obj) Gets the value of a static or instanceboolean
field.byte
Gets the value of a static or instancebyte
field.char
Gets the value of a static or instance field of typechar
or of another primitive type convertible to typechar
via a widening conversion.Class
<?> Returns theClass
object representing the class or interface that declares the field represented by thisField
object.double
Gets the value of a static or instance field of typedouble
or of another primitive type convertible to typedouble
via a widening conversion.float
Gets the value of a static or instance field of typefloat
or of another primitive type convertible to typefloat
via a widening conversion.Returns aType
object that represents the declared type for the field represented by thisField
object.int
Gets the value of a static or instance field of typeint
or of another primitive type convertible to typeint
via a widening conversion.long
Gets the value of a static or instance field of typelong
or of another primitive type convertible to typelong
via a widening conversion.int
Returns the Java language modifiers for the field represented by thisField
object, as an integer.getName()
Returns the name of the field represented by thisField
object.short
Gets the value of a static or instance field of typeshort
or of another primitive type convertible to typeshort
via a widening conversion.Class
<?> getType()
Returns aClass
object that identifies the declared type for the field represented by thisField
object.int
hashCode()
Returns a hashcode for thisField
.boolean
Returnstrue
if this field represents an element of an enumerated class; returnsfalse
otherwise.boolean
Returnstrue
if this field is a synthetic field; returnsfalse
otherwise.void
Sets the field represented by thisField
object on the specified object argument to the specified new value.void
setAccessible
(boolean flag) Set theaccessible
flag for this reflected object to the indicated boolean value.void
setBoolean
(Object obj, boolean z) Sets the value of a field as aboolean
on the specified object.void
Sets the value of a field as abyte
on the specified object.void
Sets the value of a field as achar
on the specified object.void
Sets the value of a field as adouble
on the specified object.void
Sets the value of a field as afloat
on the specified object.void
Sets the value of a field as anint
on the specified object.void
Sets the value of a field as along
on the specified object.void
Sets the value of a field as ashort
on the specified object.Returns a string describing thisField
, including its generic type.toString()
Returns a string describing thisField
.Methods declared in class java.lang.reflect.AccessibleObject
canAccess, getAnnotations, getDeclaredAnnotation, getDeclaredAnnotations, getDeclaredAnnotationsByType, isAccessible, isAnnotationPresent, setAccessible, trySetAccessible
-
Method Details
-
setAccessible
public void setAccessible(boolean flag) Description copied from class:AccessibleObject
Set theaccessible
flag for this reflected object to the indicated boolean value. A value oftrue
indicates that the reflected object should suppress checks for Java language access control when it is used. A value offalse
indicates that the reflected object should enforce checks for Java language access control when it is used, with the variation noted in the class description.This method may be used by a caller in class
C
to enable access to amember
ofdeclaring class
D
if any of the following hold:-
C
andD
are in the same module. - The member is
public
andD
ispublic
in a package that the module containingD
exports
to at least the module containingC
. - The member is
protected
static
,D
ispublic
in a package that the module containingD
exports to at least the module containingC
, andC
is a subclass ofD
. -
D
is in a package that the module containingD
opens
to at least the module containingC
. All packages in unnamed and open modules are open to all modules and so this method always succeeds whenD
is in an unnamed or open module.
This method may be used by JNI code with no caller class on the stack to enable access to a
member
ofdeclaring class
D
if and only if:- The member is
public
andD
ispublic
in a package that the module containingD
exports
unconditionally.
This method cannot be used to enable access to private members, members with default (package) access, protected instance members, or protected constructors when the declaring class is in a different module to the caller and the package containing the declaring class is not open to the caller's module.
This method cannot be used to enable write access to a non-modifiable final field. The following fields are non-modifiable:
- static final fields declared in any class or interface
- final fields declared in a hidden class
- final fields declared in a record
The
accessible
flag whentrue
suppresses Java language access control checks to only enable read access to these non-modifiable final fields.If there is a security manager, its
checkPermission
method is first called with aReflectPermission("suppressAccessChecks")
permission.- Overrides:
setAccessible
in classAccessibleObject
- Parameters:
flag
- the new value for theaccessible
flag- Throws:
InaccessibleObjectException
- if access cannot be enabledSecurityException
- if the request is denied by the security manager- External Specifications
- See Also:
-
-
getDeclaringClass
Returns theClass
object representing the class or interface that declares the field represented by thisField
object.- Specified by:
getDeclaringClass
in interfaceMember
- Returns:
- an object representing the declaring class of the underlying member
-
getName
-
getModifiers
public int getModifiers()Returns the Java language modifiers for the field represented by thisField
object, as an integer. TheModifier
class should be used to decode the modifiers.- Specified by:
getModifiers
in interfaceMember
- Returns:
- the Java language modifiers for the underlying member
- See Java Language Specification:
-
8.3 Field Declarations
9.3 Field (Constant) Declarations - See Also:
-
accessFlags
Returns an unmodifiable set of the access flags for this field, possibly empty.- Specified by:
accessFlags
in interfaceMember
- Returns:
- an unmodifiable set of the access flags for this field, possibly empty
- See Java Virtual Machine Specification:
-
4.5 Fields
- Since:
- 20
- See Also:
-
isEnumConstant
public boolean isEnumConstant()Returnstrue
if this field represents an element of an enumerated class; returnsfalse
otherwise.- Returns:
true
if and only if this field represents an element of an enumerated class.- See Java Language Specification:
-
8.9.1 Enum Constants
- Since:
- 1.5
-
isSynthetic
public boolean isSynthetic()Returnstrue
if this field is a synthetic field; returnsfalse
otherwise.- Specified by:
isSynthetic
in interfaceMember
- Returns:
- true if and only if this field is a synthetic field as defined by the Java Language Specification.
- Since:
- 1.5
- See Also:
-
getType
Returns aClass
object that identifies the declared type for the field represented by thisField
object.- Returns:
- a
Class
object identifying the declared type of the field represented by this object
-
getGenericType
Returns aType
object that represents the declared type for the field represented by thisField
object.If the declared type of the field is a parameterized type, the
Type
object returned must accurately reflect the actual type arguments used in the source code.If the type of the underlying field is a type variable or a parameterized type, it is created. Otherwise, it is resolved.
- Returns:
- a
Type
object that represents the declared type for the field represented by thisField
object - Throws:
GenericSignatureFormatError
- if the generic field signature does not conform to the format specified in The Java Virtual Machine SpecificationTypeNotPresentException
- if the generic type signature of the underlying field refers to a non-existent class or interface declarationMalformedParameterizedTypeException
- if the generic signature of the underlying field refers to a parameterized type that cannot be instantiated for any reason- Since:
- 1.5
-
equals
Compares thisField
against the specified object. Returns true if the objects are the same. TwoField
objects are the same if they were declared by the same class and have the same name and type. -
hashCode
-
toString
Returns a string describing thisField
. The format is the access modifiers for the field, if any, followed by the field type, followed by a space, followed by the fully-qualified name of the class declaring the field, followed by a period, followed by the name of the field. For example:public static final int java.lang.Thread.MIN_PRIORITY private int java.io.FileDescriptor.fd
The modifiers are placed in canonical order as specified by "The Java Language Specification". This is
public
,protected
orprivate
first, and then other modifiers in the following order:static
,final
,transient
,volatile
.- Overrides:
toString
in classObject
- Returns:
- a string describing this
Field
- See Java Language Specification:
-
8.3.1 Field Modifiers
-
toGenericString
Returns a string describing thisField
, including its generic type. The format is the access modifiers for the field, if any, followed by the generic field type, followed by a space, followed by the fully-qualified name of the class declaring the field, followed by a period, followed by the name of the field.The modifiers are placed in canonical order as specified by "The Java Language Specification". This is
public
,protected
orprivate
first, and then other modifiers in the following order:static
,final
,transient
,volatile
.- Returns:
- a string describing this
Field
, including its generic type - See Java Language Specification:
-
8.3.1 Field Modifiers
- Since:
- 1.5
-
get
Returns the value of the field represented by thisField
, on the specified object. The value is automatically wrapped in an object if it has a primitive type.The underlying field's value is obtained as follows:
If the underlying field is a static field, the
obj
argument is ignored; it may be null.Otherwise, the underlying field is an instance field. If the specified
obj
argument is null, the method throws aNullPointerException
. If the specified object is not an instance of the class or interface declaring the underlying field, the method throws anIllegalArgumentException
.If this
Field
object is enforcing Java language access control, and the underlying field is inaccessible, the method throws anIllegalAccessException
. If the underlying field is static, the class that declared the field is initialized if it has not already been initialized.Otherwise, the value is retrieved from the underlying instance or static field. If the field has a primitive type, the value is wrapped in an object before being returned, otherwise it is returned as is.
If the field is hidden in the type of
obj
, the field's value is obtained according to the preceding rules.- Parameters:
obj
- object from which the represented field's value is to be extracted- Returns:
- the value of the represented field in object
obj
; primitive values are wrapped in an appropriate object before being returned - Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof).NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.
-
getBoolean
Gets the value of a static or instanceboolean
field.- Parameters:
obj
- the object to extract theboolean
value from- Returns:
- the value of the
boolean
field - Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if the field value cannot be converted to the typeboolean
by a widening conversion.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
getByte
Gets the value of a static or instancebyte
field.- Parameters:
obj
- the object to extract thebyte
value from- Returns:
- the value of the
byte
field - Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if the field value cannot be converted to the typebyte
by a widening conversion.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
getChar
Gets the value of a static or instance field of typechar
or of another primitive type convertible to typechar
via a widening conversion.- Parameters:
obj
- the object to extract thechar
value from- Returns:
- the value of the field converted to type
char
- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if the field value cannot be converted to the typechar
by a widening conversion.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
getShort
Gets the value of a static or instance field of typeshort
or of another primitive type convertible to typeshort
via a widening conversion.- Parameters:
obj
- the object to extract theshort
value from- Returns:
- the value of the field converted to type
short
- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if the field value cannot be converted to the typeshort
by a widening conversion.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
getInt
Gets the value of a static or instance field of typeint
or of another primitive type convertible to typeint
via a widening conversion.- Parameters:
obj
- the object to extract theint
value from- Returns:
- the value of the field converted to type
int
- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if the field value cannot be converted to the typeint
by a widening conversion.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
getLong
Gets the value of a static or instance field of typelong
or of another primitive type convertible to typelong
via a widening conversion.- Parameters:
obj
- the object to extract thelong
value from- Returns:
- the value of the field converted to type
long
- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if the field value cannot be converted to the typelong
by a widening conversion.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
getFloat
Gets the value of a static or instance field of typefloat
or of another primitive type convertible to typefloat
via a widening conversion.- Parameters:
obj
- the object to extract thefloat
value from- Returns:
- the value of the field converted to type
float
- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if the field value cannot be converted to the typefloat
by a widening conversion.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
getDouble
Gets the value of a static or instance field of typedouble
or of another primitive type convertible to typedouble
via a widening conversion.- Parameters:
obj
- the object to extract thedouble
value from- Returns:
- the value of the field converted to type
double
- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if the field value cannot be converted to the typedouble
by a widening conversion.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
set
Sets the field represented by thisField
object on the specified object argument to the specified new value. The new value is automatically unwrapped if the underlying field has a primitive type.The operation proceeds as follows:
If the underlying field is static, the
obj
argument is ignored; it may be null.Otherwise the underlying field is an instance field. If the specified object argument is null, the method throws a
NullPointerException
. If the specified object argument is not an instance of the class or interface declaring the underlying field, the method throws anIllegalArgumentException
.If this
Field
object is enforcing Java language access control, and the underlying field is inaccessible, the method throws anIllegalAccessException
.If the underlying field is final, this
Field
object has write access if and only if the following conditions are met:setAccessible(true)
has succeeded for thisField
object;- the field is non-static; and
- the field's declaring class is not a hidden class; and
- the field's declaring class is not a record class.
IllegalAccessException
.Setting a final field in this way is meaningful only during deserialization or reconstruction of instances of classes with blank final fields, before they are made available for access by other parts of a program. Use in any other context may have unpredictable effects, including cases in which other parts of a program continue to use the original value of this field.
If the underlying field is of a primitive type, an unwrapping conversion is attempted to convert the new value to a value of a primitive type. If this attempt fails, the method throws an
IllegalArgumentException
.If, after possible unwrapping, the new value cannot be converted to the type of the underlying field by an identity or widening conversion, the method throws an
IllegalArgumentException
.If the underlying field is static, the class that declared the field is initialized if it has not already been initialized.
The field is set to the possibly unwrapped and widened new value.
If the field is hidden in the type of
obj
, the field's value is set according to the preceding rules.- Parameters:
obj
- the object whose field should be modifiedvalue
- the new value for the field ofobj
being modified- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is inaccessible or final; or if thisField
object has no write access.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.
-
setBoolean
public void setBoolean(Object obj, boolean z) throws IllegalArgumentException, IllegalAccessException Sets the value of a field as aboolean
on the specified object. This method is equivalent toset(obj, zObj)
, wherezObj
is aBoolean
object andzObj.booleanValue() == z
.- Parameters:
obj
- the object whose field should be modifiedz
- the new value for the field ofobj
being modified- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is either inaccessible or final; or if thisField
object has no write access.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
setByte
Sets the value of a field as abyte
on the specified object. This method is equivalent toset(obj, bObj)
, wherebObj
is aByte
object andbObj.byteValue() == b
.- Parameters:
obj
- the object whose field should be modifiedb
- the new value for the field ofobj
being modified- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is either inaccessible or final; or if thisField
object has no write access.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
setChar
Sets the value of a field as achar
on the specified object. This method is equivalent toset(obj, cObj)
, wherecObj
is aCharacter
object andcObj.charValue() == c
.- Parameters:
obj
- the object whose field should be modifiedc
- the new value for the field ofobj
being modified- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is either inaccessible or final; or if thisField
object has no write access.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
setShort
Sets the value of a field as ashort
on the specified object. This method is equivalent toset(obj, sObj)
, wheresObj
is aShort
object andsObj.shortValue() == s
.- Parameters:
obj
- the object whose field should be modifieds
- the new value for the field ofobj
being modified- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is either inaccessible or final; or if thisField
object has no write access.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
setInt
Sets the value of a field as anint
on the specified object. This method is equivalent toset(obj, iObj)
, whereiObj
is anInteger
object andiObj.intValue() == i
.- Parameters:
obj
- the object whose field should be modifiedi
- the new value for the field ofobj
being modified- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is either inaccessible or final; or if thisField
object has no write access.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
setLong
Sets the value of a field as along
on the specified object. This method is equivalent toset(obj, lObj)
, wherelObj
is aLong
object andlObj.longValue() == l
.- Parameters:
obj
- the object whose field should be modifiedl
- the new value for the field ofobj
being modified- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is either inaccessible or final; or if thisField
object has no write access.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
setFloat
Sets the value of a field as afloat
on the specified object. This method is equivalent toset(obj, fObj)
, wherefObj
is aFloat
object andfObj.floatValue() == f
.- Parameters:
obj
- the object whose field should be modifiedf
- the new value for the field ofobj
being modified- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is either inaccessible or final; or if thisField
object has no write access.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
setDouble
Sets the value of a field as adouble
on the specified object. This method is equivalent toset(obj, dObj)
, wheredObj
is aDouble
object anddObj.doubleValue() == d
.- Parameters:
obj
- the object whose field should be modifiedd
- the new value for the field ofobj
being modified- Throws:
IllegalAccessException
- if thisField
object is enforcing Java language access control and the underlying field is either inaccessible or final; or if thisField
object has no write access.IllegalArgumentException
- if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof), or if an unwrapping conversion fails.NullPointerException
- if the specified object is null and the field is an instance field.ExceptionInInitializerError
- if the initialization provoked by this method fails.- See Also:
-
getAnnotation
Returns this element's annotation for the specified type if such an annotation is present, else null.Note that any annotation returned by this method is a declaration annotation.
- Specified by:
getAnnotation
in interfaceAnnotatedElement
- Overrides:
getAnnotation
in classAccessibleObject
- Type Parameters:
T
- the type of the annotation to query for and return if present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- this element's annotation for the specified annotation type if present on this element, else null
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.5
-
getAnnotationsByType
Returns annotations that are associated with this element. If there are no annotations associated with this element, the return value is an array of length 0. The difference between this method andAnnotatedElement.getAnnotation(Class)
is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getAnnotationsByType
in interfaceAnnotatedElement
- Overrides:
getAnnotationsByType
in classAccessibleObject
- Type Parameters:
T
- the type of the annotation to query for and return if present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- all this element's annotations for the specified annotation type if associated with this element, else an array of length zero
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.8
-
getAnnotatedType
Returns an AnnotatedType object that represents the use of a type to specify the declared type of the field represented by this Field.- Returns:
- an object representing the declared type of the field represented by this Field
- Since:
- 1.8
-