public final class Field extends AccessibleObject implements 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.
Modifier and Type | Method and Description |
---|---|
boolean |
equals(Object obj)
Compares this
Field against the specified object. |
Object |
get(Object obj)
Returns the value of the field represented by this
Field , on
the specified object. |
<T extends Annotation> |
getAnnotation(Class<T> annotationClass)
Returns this element's annotation for the specified type if
such an annotation is present, else null.
|
boolean |
getBoolean(Object obj)
Gets the value of a static or instance
boolean field. |
byte |
getByte(Object obj)
Gets the value of a static or instance
byte field. |
char |
getChar(Object obj)
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. |
Annotation[] |
getDeclaredAnnotations()
Returns all annotations that are directly present on this
element.
|
Class<?> |
getDeclaringClass()
Returns the
Class object representing the class or interface
that declares the field represented by this Field object. |
double |
getDouble(Object obj)
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. |
float |
getFloat(Object obj)
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. |
Type |
getGenericType()
Returns a
Type object that represents the declared type for
the field represented by this Field object. |
int |
getInt(Object obj)
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. |
long |
getLong(Object obj)
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. |
int |
getModifiers()
Returns the Java language modifiers for the field represented
by this
Field object, as an integer. |
String |
getName()
Returns the name of the field represented by this
Field object. |
short |
getShort(Object obj)
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. |
Class<?> |
getType()
Returns a
Class object that identifies the
declared type for the field represented by this
Field object. |
int |
hashCode()
Returns a hashcode for this
Field . |
boolean |
isEnumConstant()
Returns
true if this field represents an element of
an enumerated type; returns false otherwise. |
boolean |
isSynthetic()
Returns
true if this field is a synthetic
field; returns false otherwise. |
void |
set(Object obj,
Object value)
Sets the field represented by this
Field object on the
specified object argument to the specified new value. |
void |
setBoolean(Object obj,
boolean z)
Sets the value of a field as a
boolean on the specified object. |
void |
setByte(Object obj,
byte b)
Sets the value of a field as a
byte on the specified object. |
void |
setChar(Object obj,
char c)
Sets the value of a field as a
char on the specified object. |
void |
setDouble(Object obj,
double d)
Sets the value of a field as a
double on the specified object. |
void |
setFloat(Object obj,
float f)
Sets the value of a field as a
float on the specified object. |
void |
setInt(Object obj,
int i)
Sets the value of a field as an
int on the specified object. |
void |
setLong(Object obj,
long l)
Sets the value of a field as a
long on the specified object. |
void |
setShort(Object obj,
short s)
Sets the value of a field as a
short on the specified object. |
String |
toGenericString()
Returns a string describing this
Field , including
its generic type. |
String |
toString()
Returns a string describing this
Field . |
getAnnotations, isAccessible, isAnnotationPresent, setAccessible, setAccessible
public Class<?> getDeclaringClass()
Class
object representing the class or interface
that declares the field represented by this Field
object.getDeclaringClass
in interface Member
public String getName()
Field
object.public int getModifiers()
Field
object, as an integer. The Modifier
class should
be used to decode the modifiers.getModifiers
in interface Member
Modifier
public boolean isEnumConstant()
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.public boolean isSynthetic()
true
if this field is a synthetic
field; returns false
otherwise.isSynthetic
in interface Member
public Class<?> getType()
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 objectpublic Type getGenericType()
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 SpecificationTypeNotPresentException
- if the generic type
signature of the underlying field refers to a non-existent
type declarationMalformedParameterizedTypeException
- if the generic
signature of the underlying field refers to a parameterized type
that cannot be instantiated for any reasonpublic boolean equals(Object obj)
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.equals
in class Object
obj
- the reference object with which to compare.true
if this object is the same as the obj
argument; false
otherwise.Object.hashCode()
,
HashMap
public int hashCode()
Field
. This is computed as the
exclusive-or of the hashcodes for the underlying field's
declaring class name and its name.hashCode
in class Object
Object.equals(java.lang.Object)
,
System.identityHashCode(java.lang.Object)
public String toString()
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
.
public String toGenericString()
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 typepublic Object get(Object obj) throws IllegalArgumentException, IllegalAccessException
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 is enforcing 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 extractedobj
; primitive values are wrapped in an appropriate
object before being returnedIllegalAccessException
- if this Field
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.public boolean getBoolean(Object obj) throws IllegalArgumentException, IllegalAccessException
boolean
field.obj
- the object to extract the boolean
value
fromboolean
fieldIllegalAccessException
- if this Field
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 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.get(java.lang.Object)
public byte getByte(Object obj) throws IllegalArgumentException, IllegalAccessException
byte
field.obj
- the object to extract the byte
value
frombyte
fieldIllegalAccessException
- if this Field
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 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.get(java.lang.Object)
public char getChar(Object obj) throws IllegalArgumentException, IllegalAccessException
char
or of another primitive type convertible to
type char
via a widening conversion.obj
- the object to extract the char
value
fromchar
IllegalAccessException
- if this Field
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 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.get(java.lang.Object)
public short getShort(Object obj) throws IllegalArgumentException, IllegalAccessException
short
or of another primitive type convertible to
type short
via a widening conversion.obj
- the object to extract the short
value
fromshort
IllegalAccessException
- if this Field
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 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.get(java.lang.Object)
public int getInt(Object obj) throws IllegalArgumentException, IllegalAccessException
int
or of another primitive type convertible to
type int
via a widening conversion.obj
- the object to extract the int
value
fromint
IllegalAccessException
- if this Field
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 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.get(java.lang.Object)
public long getLong(Object obj) throws IllegalArgumentException, IllegalAccessException
long
or of another primitive type convertible to
type long
via a widening conversion.obj
- the object to extract the long
value
fromlong
IllegalAccessException
- if this Field
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 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.get(java.lang.Object)
public float getFloat(Object obj) throws IllegalArgumentException, IllegalAccessException
float
or of another primitive type convertible to
type float
via a widening conversion.obj
- the object to extract the float
value
fromfloat
IllegalAccessException
- if this Field
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 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.get(java.lang.Object)
public double getDouble(Object obj) throws IllegalArgumentException, IllegalAccessException
double
or of another primitive type convertible to
type double
via a widening conversion.obj
- the object to extract the double
value
fromdouble
IllegalAccessException
- if this Field
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 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.get(java.lang.Object)
public void set(Object obj, Object value) throws IllegalArgumentException, IllegalAccessException
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 is enforcing 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
object
and the 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 modifiedvalue
- the new value for the field of obj
being modifiedIllegalAccessException
- if this Field
object
is enforcing Java language access control and the underlying
field is either inaccessible or final.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.public void setBoolean(Object obj, boolean z) throws IllegalArgumentException, IllegalAccessException
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 modifiedz
- the new value for the field of obj
being modifiedIllegalAccessException
- if this Field
object
is enforcing Java language access control and the underlying
field is either inaccessible or final.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.set(java.lang.Object, java.lang.Object)
public void setByte(Object obj, byte b) throws IllegalArgumentException, IllegalAccessException
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 modifiedb
- the new value for the field of obj
being modifiedIllegalAccessException
- if this Field
object
is enforcing Java language access control and the underlying
field is either inaccessible or final.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.set(java.lang.Object, java.lang.Object)
public void setChar(Object obj, char c) throws IllegalArgumentException, IllegalAccessException
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 modifiedc
- the new value for the field of obj
being modifiedIllegalAccessException
- if this Field
object
is enforcing Java language access control and the underlying
field is either inaccessible or final.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.set(java.lang.Object, java.lang.Object)
public void setShort(Object obj, short s) throws IllegalArgumentException, IllegalAccessException
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 modifieds
- the new value for the field of obj
being modifiedIllegalAccessException
- if this Field
object
is enforcing Java language access control and the underlying
field is either inaccessible or final.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.set(java.lang.Object, java.lang.Object)
public void setInt(Object obj, int i) throws IllegalArgumentException, IllegalAccessException
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 modifiedi
- the new value for the field of obj
being modifiedIllegalAccessException
- if this Field
object
is enforcing Java language access control and the underlying
field is either inaccessible or final.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.set(java.lang.Object, java.lang.Object)
public void setLong(Object obj, long l) throws IllegalArgumentException, IllegalAccessException
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 modifiedl
- the new value for the field of obj
being modifiedIllegalAccessException
- if this Field
object
is enforcing Java language access control and the underlying
field is either inaccessible or final.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.set(java.lang.Object, java.lang.Object)
public void setFloat(Object obj, float f) throws IllegalArgumentException, IllegalAccessException
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 modifiedf
- the new value for the field of obj
being modifiedIllegalAccessException
- if this Field
object
is enforcing Java language access control and the underlying
field is either inaccessible or final.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.set(java.lang.Object, java.lang.Object)
public void setDouble(Object obj, double d) throws IllegalArgumentException, IllegalAccessException
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 modifiedd
- the new value for the field of obj
being modifiedIllegalAccessException
- if this Field
object
is enforcing Java language access control and the underlying
field is either inaccessible or final.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.set(java.lang.Object, java.lang.Object)
public <T extends Annotation> T getAnnotation(Class<T> annotationClass)
AnnotatedElement
getAnnotation
in interface AnnotatedElement
getAnnotation
in class AccessibleObject
annotationClass
- the Class object corresponding to the
annotation typeNullPointerException
- if the given annotation class is nullpublic Annotation[] getDeclaredAnnotations()
AnnotatedElement
getDeclaredAnnotations
in interface AnnotatedElement
getDeclaredAnnotations
in class AccessibleObject
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