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. |
AnnotatedType |
getAnnotatedType()
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> |
getAnnotation(Class<T> annotationClass)
Returns this element's annotation for the specified type if
such an annotation is present, else null.
|
<T extends Annotation> |
getAnnotationsByType(Class<T> annotationClass)
Returns annotations that are associated with this element.
|
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 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, getDeclaredAnnotation, getDeclaredAnnotationsByType, isAccessible, isAnnotationPresent, setAccessible, setAccessiblepublic Class<?> getDeclaringClass()
Class object representing the class or interface
that declares the field represented by this Field object.getDeclaringClass in interface Memberpublic 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 MemberModifierpublic 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 Memberpublic 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 Objectobj - the reference object with which to compare.true if this object is the same as the obj
argument; false otherwise.Object.hashCode(),
HashMappublic 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 ObjectObject.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
fromcharIllegalAccessException - 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
fromshortIllegalAccessException - 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
fromintIllegalAccessException - 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
fromlongIllegalAccessException - 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
fromfloatIllegalAccessException - 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
fromdoubleIllegalAccessException - 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)
AnnotatedElementgetAnnotation in interface AnnotatedElementgetAnnotation in class AccessibleObjectT - the type of the annotation to query for and return if presentannotationClass - the Class object corresponding to the
annotation typeNullPointerException - if the given annotation class is nullpublic <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass)
AnnotatedElement.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.getAnnotationsByType in interface AnnotatedElementgetAnnotationsByType in class AccessibleObjectT - the type of the annotation to query for and return if presentannotationClass - the Class object corresponding to the
annotation typeNullPointerException - if the given annotation class is nullpublic Annotation[] getDeclaredAnnotations()
getDeclaredAnnotations in interface AnnotatedElementgetDeclaredAnnotations in class AccessibleObjectpublic AnnotatedType getAnnotatedType()
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