java.lang.Object | ||
↳ | java.lang.reflect.AccessibleObject | |
↳ | java.lang.reflect.Field |
A 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.
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Inherited Constants | |||||||||||
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From interface
java.lang.reflect.Member
|
Public Methods | |||||||||||
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Compares this
Field against the specified object. | |||||||||||
Returns the value of the field represented by this
Field , on
the specified object. | |||||||||||
Returns this element's annotation for the specified type if
such an annotation is present, else null.
| |||||||||||
Gets the value of a static or instance
boolean field. | |||||||||||
Gets the value of a static or instance
byte field. | |||||||||||
Gets the value of a static or instance field of type
char or of another primitive type convertible to
type char via a widening conversion. | |||||||||||
Returns all annotations that are directly present on this
element.
| |||||||||||
Returns the
Class object representing the class or interface
that declares the field represented by this Field object. | |||||||||||
Gets the value of a static or instance field of type
double or of another primitive type convertible to
type double via a widening conversion. | |||||||||||
Gets the value of a static or instance field of type
float or of another primitive type convertible to
type float via a widening conversion. | |||||||||||
Returns a
Type object that represents the declared type for
the field represented by this Field object. | |||||||||||
Gets the value of a static or instance field of type
int or of another primitive type convertible to
type int via a widening conversion. | |||||||||||
Gets the value of a static or instance field of type
long or of another primitive type convertible to
type long via a widening conversion. | |||||||||||
Returns the Java language modifiers for the field represented
by this
Field object, as an integer. | |||||||||||
Returns the name of the field represented by this
Field object. | |||||||||||
Gets the value of a static or instance field of type
short or of another primitive type convertible to
type short via a widening conversion. | |||||||||||
Returns a
Class object that identifies the
declared type for the field represented by this
Field object. | |||||||||||
Returns a hashcode for this
Field . | |||||||||||
Returns
true if this field represents an element of
an enumerated type; returns false otherwise. | |||||||||||
Returns
true if this field is a synthetic
field; returns false otherwise. | |||||||||||
Sets the field represented by this
Field object on the
specified object argument to the specified new value. | |||||||||||
Sets the value of a field as a
boolean on the specified object. | |||||||||||
Sets the value of a field as a
byte on the specified object. | |||||||||||
Sets the value of a field as a
char on the specified object. | |||||||||||
Sets the value of a field as a
double on the specified object. | |||||||||||
Sets the value of a field as a
float on the specified object. | |||||||||||
Sets the value of a field as an
int on the specified object. | |||||||||||
Sets the value of a field as a
long on the specified object. | |||||||||||
Sets the value of a field as a
short on the specified object. | |||||||||||
Returns a string describing this
Field , including
its generic type. | |||||||||||
Returns a string describing this
Field . |
[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.reflect.AccessibleObject
| |||||||||||
From class
java.lang.Object
| |||||||||||
From interface
java.lang.reflect.AnnotatedElement
| |||||||||||
From interface
java.lang.reflect.Member
|
Compares this Field
against the specified object. Returns
true if the objects are the same. Two Field
objects are the same if
they were declared by the same class and have the same name
and type.
obj | the reference object with which to compare. |
---|
true
if this object is the same as the obj
argument; false
otherwise.Returns the value of the field represented by this Field
, 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 a
NullPointerException
. If the specified object is not an
instance of the class or interface declaring the underlying
field, the method throws an IllegalArgumentException
.
If this Field
object enforces Java language access control, and
the underlying field is inaccessible, the method throws an
IllegalAccessException
.
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.
obj | object from which the represented field's value is to be extracted |
---|
obj
; primitive values are wrapped in an appropriate
object before being returnedIllegalAccessException | if the underlying field is inaccessible. |
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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. |
Returns this element's annotation for the specified type if such an annotation is present, else null.
annotationClass | the Class object corresponding to the annotation type |
---|
NullPointerException |
---|
Gets the value of a static or instance boolean
field.
obj | the object to extract the boolean value
from |
---|
boolean
fieldIllegalAccessException | if 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 type boolean 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. |
Gets the value of a static or instance byte
field.
obj | the object to extract the byte value
from |
---|
byte
fieldIllegalAccessException | if 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 type byte 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. |
Gets the value of a static or instance field of type
char
or of another primitive type convertible to
type char
via a widening conversion.
obj | the object to extract the char value
from |
---|
char
IllegalAccessException | if 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 type char 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. |
Returns all annotations that are directly present on this element. Unlike the other methods in this interface, this method ignores inherited annotations. (Returns an array of length zero if no annotations are directly present on this element.) The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
Returns the Class
object representing the class or interface
that declares the field represented by this Field
object.
Gets the value of a static or instance field of type
double
or of another primitive type convertible to
type double
via a widening conversion.
obj | the object to extract the double value
from |
---|
double
IllegalAccessException | if 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 type double 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. |
Gets the value of a static or instance field of type
float
or of another primitive type convertible to
type float
via a widening conversion.
obj | the object to extract the float value
from |
---|
float
IllegalAccessException | if 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 type float 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. |
Returns a Type
object that represents the declared type for
the field represented by this Field
object.
If the Type
is a parameterized type, the
Type
object returned must accurately reflect the
actual type parameters 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.
Type
object that represents the declared type for
the field represented by this Field
objectGenericSignatureFormatError | if the generic field signature does not conform to the format specified in the Java Virtual Machine Specification, 3rd edition |
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TypeNotPresentException | if the generic type signature of the underlying field refers to a non-existent type declaration |
MalformedParameterizedTypeException | if the generic signature of the underlying field refers to a parameterized type that cannot be instantiated for any reason |
Gets the value of a static or instance field of type
int
or of another primitive type convertible to
type int
via a widening conversion.
obj | the object to extract the int value
from |
---|
int
IllegalAccessException | if 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 type int 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. |
Gets the value of a static or instance field of type
long
or of another primitive type convertible to
type long
via a widening conversion.
obj | the object to extract the long value
from |
---|
long
IllegalAccessException | if 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 type long 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. |
Returns the Java language modifiers for the field represented
by this Field
object, as an integer. The Modifier
class should
be used to decode the modifiers.
Returns the name of the field represented by this Field
object.
Gets the value of a static or instance field of type
short
or of another primitive type convertible to
type short
via a widening conversion.
obj | the object to extract the short value
from |
---|
short
IllegalAccessException | if 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 type short 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. |
Returns a Class
object that identifies the
declared type for the field represented by this
Field
object.
Class
object identifying the declared
type of the field represented by this object
Returns a hashcode for this Field
. This is computed as the
exclusive-or of the hashcodes for the underlying field's
declaring class name and its name.
Returns true
if this field represents an element of
an enumerated type; returns false
otherwise.
true
if and only if this field represents an element of
an enumerated type.Returns true
if this field is a synthetic
field; returns false
otherwise.
Sets the field represented by this Field
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 an IllegalArgumentException
.
If this Field
object enforces Java language access control, and
the underlying field is inaccessible, the method throws an
IllegalAccessException
.
If the underlying field is final, the method throws an
IllegalAccessException
unless
setAccessible(true)
has succeeded for this field
and this field is non-static. 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.
obj | the object whose field should be modified |
---|---|
value | the new value for the field of obj
being modified |
IllegalAccessException | if 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 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. |
Sets the value of a field as a boolean
on the specified object.
This method is equivalent to
set(obj, zObj)
,
where zObj
is a Boolean
object and
zObj.booleanValue() == z
.
obj | the object whose field should be modified |
---|---|
z | the new value for the field of obj
being modified |
IllegalAccessException | if 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 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. |
Sets the value of a field as a byte
on the specified object.
This method is equivalent to
set(obj, bObj)
,
where bObj
is a Byte
object and
bObj.byteValue() == b
.
obj | the object whose field should be modified |
---|---|
b | the new value for the field of obj
being modified |
IllegalAccessException | if 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 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. |
Sets the value of a field as a char
on the specified object.
This method is equivalent to
set(obj, cObj)
,
where cObj
is a Character
object and
cObj.charValue() == c
.
obj | the object whose field should be modified |
---|---|
c | the new value for the field of obj
being modified |
IllegalAccessException | if 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 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. |
Sets the value of a field as a double
on the specified object.
This method is equivalent to
set(obj, dObj)
,
where dObj
is a Double
object and
dObj.doubleValue() == d
.
obj | the object whose field should be modified |
---|---|
d | the new value for the field of obj
being modified |
IllegalAccessException | if 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 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. |
Sets the value of a field as a float
on the specified object.
This method is equivalent to
set(obj, fObj)
,
where fObj
is a Float
object and
fObj.floatValue() == f
.
obj | the object whose field should be modified |
---|---|
f | the new value for the field of obj
being modified |
IllegalAccessException | if 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 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. |
Sets the value of a field as an int
on the specified object.
This method is equivalent to
set(obj, iObj)
,
where iObj
is a Integer
object and
iObj.intValue() == i
.
obj | the object whose field should be modified |
---|---|
i | the new value for the field of obj
being modified |
IllegalAccessException | if 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 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. |
Sets the value of a field as a long
on the specified object.
This method is equivalent to
set(obj, lObj)
,
where lObj
is a Long
object and
lObj.longValue() == l
.
obj | the object whose field should be modified |
---|---|
l | the new value for the field of obj
being modified |
IllegalAccessException | if 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 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. |
Sets the value of a field as a short
on the specified object.
This method is equivalent to
set(obj, sObj)
,
where sObj
is a Short
object and
sObj.shortValue() == s
.
obj | the object whose field should be modified |
---|---|
s | the new value for the field of obj
being modified |
IllegalAccessException | if 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 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. |
Returns a string describing this Field
, 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
or private
first, and then other
modifiers in the following order: static
, final
,
transient
, volatile
.
Field
, including
its generic typeReturns a string describing this Field
. 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
or private
first, and then other
modifiers in the following order: static
, final
,
transient
, volatile
.