Class java.lang.reflect.Field





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Class java.lang.reflect.Field


java.lang.Object
|
+----java.lang.reflect.Field



public final class Field
extends Object
implements Member

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.


See Also:
Member, Class, getFields, getField, getDeclaredFields, getDeclaredField








equals(Object)
Compares this Field against the specified object.

get(Object)
Returns the value of the field represented by this Field, on
the specified object.

getBoolean(Object)
Get the value of a field as a boolean on specified object.

getByte(Object)
Get the value of a field as a byte on specified object.

getChar(Object)
Get the value of a field as a char on specified object.

getDeclaringClass()
Returns the Class object representing the class or interface
that declares the field represented by this Field object.

getDouble(Object)
Get the value of a field as a double on specified object.

getFloat(Object)
Get the value of a field as a float on specified object.

getInt(Object)
Get the value of a field as a int on specified object.

getLong(Object)
Get the value of a field as a long on specified object.

getModifiers()
Returns the Java language modifiers for the field represented
by this Field object, as an integer.

getName()
Returns the name of the field represented by this Field object.

getShort(Object)
Get the value of a field as a short on specified object.

getType()
Returns a Class object that identifies the declared type for
the field represented by this Field object.

hashCode()
Returns a hashcode for this Field.

set(Object, Object)
Sets the field represented by this Field object on the
specified object argument to the specified new value.

setBoolean(Object, boolean)
Set the value of a field as a boolean on specified object.

setByte(Object, byte)
Set the value of a field as a byte on specified object.

setChar(Object, char)
Set the value of a field as a char on specified object.

setDouble(Object, double)
Set the value of a field as a double on specified object.

setFloat(Object, float)
Set the value of a field as a float on specified object.

setInt(Object, int)
Set the value of a field as an int on specified object.

setLong(Object, long)
Set the value of a field as a long on specified object.

setShort(Object, short)
Set the value of a field as a short on specified object.

toString()
Return a string describing this Field.






getDeclaringClass

public Class getDeclaringClass()


Returns the Class object representing the class or interface
that declares the field represented by this Field object.



getName

public String getName()


Returns the name of the field represented by this Field object.



getModifiers

public native int getModifiers()


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.


See Also:
Modifier



getType

public Class getType()


Returns a Class object that identifies the declared type for
the field represented by this Field object.



equals

public boolean equals(Object obj)


Compares this Field against the specified object. Returns
true if the objects are the same. Two Fields are the same if
they were declared by the same class and have the same name
and type.


Overrides:
equals in class Object



hashCode

public int hashCode()


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.


Overrides:
hashCode in class Object



toString

public String toString()


Return 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.


Overrides:
toString in class Object



get

public native Object get(Object obj) throws IllegalArgumentException, IllegalAccessException


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 object 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 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.
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.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field.
Throws: NullPointerException
if the specified object is null.



getBoolean

public native boolean getBoolean(Object obj) throws IllegalArgumentException, IllegalAccessException


Get the value of a field as a boolean on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the field value cannot be
converted to the return type by a widening conversion.
See Also:
get



getByte

public native byte getByte(Object obj) throws IllegalArgumentException, IllegalAccessException


Get the value of a field as a byte on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the field value cannot be
converted to the return type by a widening conversion.
See Also:
get



getChar

public native char getChar(Object obj) throws IllegalArgumentException, IllegalAccessException


Get the value of a field as a char on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the field value cannot be
converted to the return type by a widening conversion.
See Also:
get



getShort

public native short getShort(Object obj) throws IllegalArgumentException, IllegalAccessException


Get the value of a field as a short on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the field value cannot be
converted to the return type by a widening conversion.
See Also:
get



getInt

public native int getInt(Object obj) throws IllegalArgumentException, IllegalAccessException


Get the value of a field as a int on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the field value cannot be
converted to the return type by a widening conversion.
See Also:
get



getLong

public native long getLong(Object obj) throws IllegalArgumentException, IllegalAccessException


Get the value of a field as a long on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the field value cannot be
converted to the return type by a widening conversion.
See Also:
get



getFloat

public native float getFloat(Object obj) throws IllegalArgumentException, IllegalAccessException


Get the value of a field as a float on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the field value cannot be
converted to the return type by a widening conversion.
See Also:
get



getDouble

public native double getDouble(Object obj) throws IllegalArgumentException, IllegalAccessException


Get the value of a field as a double on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the field value cannot be
converted to the return type by a widening conversion.
See Also:
get



set

public native void set(Object obj,
Object value) throws IllegalArgumentException, IllegalAccessException


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 object 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.
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.
The field is set to the possibly unwrapped and widened new value.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field, or if an unwrapping conversion fails.
Throws: NullPointerException
if the specified object is null.



setBoolean

public native void setBoolean(Object obj,
boolean z) throws IllegalArgumentException, IllegalAccessException


Set the value of a field as a boolean on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field, or if an unwrapping conversion fails.
See Also:
set



setByte

public native void setByte(Object obj,
byte b) throws IllegalArgumentException, IllegalAccessException


Set the value of a field as a byte on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field, or if an unwrapping conversion fails.
See Also:
set



setChar

public native void setChar(Object obj,
char c) throws IllegalArgumentException, IllegalAccessException


Set the value of a field as a char on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field, or if an unwrapping conversion fails.
See Also:
set



setShort

public native void setShort(Object obj,
short s) throws IllegalArgumentException, IllegalAccessException


Set the value of a field as a short on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field, or if an unwrapping conversion fails.
See Also:
set



setInt

public native void setInt(Object obj,
int i) throws IllegalArgumentException, IllegalAccessException


Set the value of a field as an int on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field, or if an unwrapping conversion fails.
See Also:
set



setLong

public native void setLong(Object obj,
long l) throws IllegalArgumentException, IllegalAccessException


Set the value of a field as a long on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field, or if an unwrapping conversion fails.
See Also:
set



setFloat

public native void setFloat(Object obj,
float f) throws IllegalArgumentException, IllegalAccessException


Set the value of a field as a float on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field, or if an unwrapping conversion fails.
See Also:
set



setDouble

public native void setDouble(Object obj,
double d) throws IllegalArgumentException, IllegalAccessException


Set the value of a field as a double on specified object.


Throws: IllegalAccessException
if the underlying constructor
is inaccessible.
Throws: IllegalArgumentException
if the specified object is not an
instance of the class or interface declaring the underlying
field, or if an unwrapping conversion fails.
See Also:
set




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