java.lang.Object
java.lang.reflect.AccessibleObject
java.lang.reflect.Field
public final class 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.
Member, Class, Class.getFields(), Class.getField(String), Class.getDeclaredFields(), Class.getDeclaredField(String)
boolean equals(Object obj)
Field against the specified object. Object get(Object obj)
Field, on the specified object. <T extends Annotation>
T getAnnotation(Class<T> annotationClass)
boolean getBoolean(Object obj)
boolean field. byte getByte(Object obj)
byte field. char getChar(Object obj)
char or of another primitive type convertible to type char via a widening conversion. Annotation[] getDeclaredAnnotations()
Class<?> getDeclaringClass()
Class object representing the class or interface that declares the field represented by this Field object. double getDouble(Object obj)
double or of another primitive type convertible to type double via a widening conversion. float getFloat(Object obj)
float or of another primitive type convertible to type float via a widening conversion. Type getGenericType()
int getInt(Object obj)
int or of another primitive type convertible to type int via a widening conversion. long getLong(Object obj)
long or of another primitive type convertible to type long via a widening conversion. int getModifiers()
Field object, as an integer. String getName()
Field object. short getShort(Object obj)
short or of another primitive type convertible to type short via a widening conversion. Class<?> getType()
Class object that identifies the declared type for the field represented by this Field object. int hashCode()
Field. boolean isEnumConstant()
boolean isSynthetic()
void set(Object obj, Object value)
Field object on the specified object argument to the specified new value. void setBoolean(Object obj, boolean z)
boolean on the specified object. void setByte(Object obj, byte b)
byte on the specified object. void setChar(Object obj, char c)
char on the specified object. void setDouble(Object obj, double d)
double on the specified object. void setFloat(Object obj, float f)
float on the specified object. void setInt(Object obj, int i)
int on the specified object. void setLong(Object obj, long l)
long on the specified object. void setShort(Object obj, short s)
short on the specified object. String toGenericString()
Field, including its generic type. String toString()
Field. getDeclaringClass
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.
getName in interface Member
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()
public boolean isSynthetic()
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 object
public Type getGenericType()
If the Type is a parameterized type, the Type object returned must accurately reflect the actual type parameters used in the source code.
If an the type of the underlying field is a type variable or a parameterized type, it is created. Otherwise, it is resolved.
GenericSignatureFormatError - if the generic field signature does not conform to the format specified in the Java Virtual Machine Specification, 3rd edition
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
public 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(), Hashtable
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), Hashtable
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.
toString in class Object
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 type
public 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 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
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).
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 from
boolean field
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 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 from
byte field
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 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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 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.
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 type
public Annotation[] getDeclaredAnnotations()
AnnotatedElement
getDeclaredAnnotations in interface AnnotatedElement
getDeclaredAnnotations in class AccessibleObject
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