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Apackage java.lang.reflect;public final class Field extends Object implements Member
Field provides information about, and access to, a single field of a class or
interface. The reflected field may be a class variable (static field) or an
instance variable (instance field).
Only the Java Virtual Machine may create Field objects; user code obtains
Field references via the methods getField, getFields, getDeclaredField,
and getDeclaredFields of class Class.
A Field permits widening conversions to occur during get or set operations,
but throws an IllegalArgumentException if a narrowing conversion would
occur.
public Class getDeclaringClass()
Returns the Class object representing the class or interface that declares the
field represented by this Field object.
public String getName()
Returns the simple name of the field represented by this Field object.
public int getModifiers()
Returns the Java language modifiers for the field represented by this Field
object, encoded in an integer. The Modifier class should be used to decode the
modifiers.
The modifier encodings are defined in The Java Virtual Machine Specification, Table 4.3.
public Class getType()
Returns a Class object that identifies the declared type for the field
represented by this Field object.
public boolean equals(Object obj)
Compares this Field against the specified Object. Returns true if they are
the same; false otherwise. Two Field objects are the same if they have the
same declaring class and the same name.
This method overrides the equals method of class Object.
public int hashCode()
Returns a hashcode for this Field object. This is computed as the exclusive-or
of the hashcodes for the Field's declaring class name and its simple name.
This method overrides the hashCode method of class Object.
public String toString()
Returns a String object describing this Field. The format is the Java language
modifiers for the represented 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 in The Java Language
Specification. This is public, protected, or private first, and then other
modifiers in the following order: static, final, transient, and volatile.
This method overrides the toString method of class Object.
Returns the value of the field represented by thispublic Object get(Object obj)throws NullPointerException, 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:
static field, the object argument is ignored; it
may be null.
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.
Field object enforces Java language access control, and the
underlying field is inaccessible, the method throws an
IllegalAccessException.
Field.get are also provided for efficiency; these avoid
the final wrapping conversion. They are described below.
Returns the value of the field represented by thispublic boolean getBoolean(Object obj)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object, as a boolean. See Field.get for the detailed procedure.
If the underlying field is not of type boolean, the method throws an
IllegalArgumentException.
Returns the value of the field represented by thispublic byte getByte(Object obj)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object, as a byte. See Field.get for the detailed procedure.
If the underlying field is not of type byte, the method throws an
IllegalArgumentException.
Returns the value of the field represented by thispublic char getChar(Object obj)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object, as a char. See Field.get for the detailed procedure.
If the underlying field's value is not of type char, the method throws an
IllegalArgumentException.
Returns the value of the field represented by thispublic short getShort(Object obj)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object, as a short. See Field.get for the detailed procedure.
If the underlying field's value cannot be converted to a short by an identity or
a widening conversion, the method throws an IllegalArgumentException.
Returns the value of the field represented by thispublic int getInt(Object obj)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object, as an int. See Field.get for the detailed procedure.
If the underlying field's value cannot be converted to an int by an identity or
a widening conversion, the method throws an IllegalArgumentException.
Returns the value of the field represented by thispublic long getLong(Object obj)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object, as a long. See Field.get for the detailed procedure.
If the underlying field's value cannot be converted to a long by an identity or
a widening conversion, the method throws an IllegalArgumentException.
Returns the value of the field represented by thispublic float getFloat(Object obj)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object, as a float. See Field.get for the detailed procedure.
If the underlying field's value cannot be converted to a float by an identity or
a widening conversion, the method throws an IllegalArgumentException.
Returns the value of the field represented by thispublic double getDouble(Object obj)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object, as a double. See Field.get for the detailed procedure.
If the underlying field's value cannot be converted to a double by an identity
or a widening conversion, the method throws an IllegalArgumentException.
Sets the field represented by thispublic void set(Object obj, Object value)throws NullPointerException, 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:
static field, the object argument is ignored; it
may be null.
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.
Field object enforces Java language access control, and the
underlying field is inaccessible, the method throws an
IllegalAccessException.
final field, the method throws an
IllegalAccessException.
null, the conversion fails by throwing a
NullPointerException. If the new object value is not an instance of a
standard Java wrapper class, the conversion fails by throwing an
IllegalArgumentException.
IllegalArgumentException.
Field.set are also provided for efficiency; these let
application code avoid having to wrap the new field value. They are described
below.
Sets the value of the field represented by thispublic void setBoolean(Object obj, boolean z)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object argument to the specified boolean value. See Field.set for the detailed
procedure.
If the underlying field is not of type boolean, the method throws an
IllegalArgumentException.
Sets the value of the field represented by thispublic void setByte(Object obj, byte b)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object argument to the specified byte value. See Field.set for the detailed
procedure.
If the new value cannot be converted to the type of the underlying field by an
identity or a widening conversion, the method throws an
IllegalArgumentException.
Sets the value of the field represented by thispublic void setChar(Object obj, char c)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object argument to the specified char value. See Field.set for the detailed
procedure.
If the new value cannot be converted to the type of the underlying field by an
identity or a widening conversion, the method throws an
IllegalArgumentException.
Sets the value of the field represented by thispublic void setShort(Object obj, short s)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object argument to the specified short value. See Field.set for the detailed
procedure.
If the new value cannot be converted to the type of the underlying field by an
identity or a widening conversion, the method throws an
IllegalArgumentException.
Sets the value of the field represented by thispublic void setInt(Object obj, int i)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object argument to the specified int value. See Field.set for the detailed
procedure.
If the new value cannot be converted to the type of the underlying field by an
identity or a widening conversion, the method throws an
IllegalArgumentException.
Sets the value of the field represented by thispublic void setLong(Object obj, long l)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object argument to the specified long value. See Field.set for the detailed
procedure.
If the new value cannot be converted to the type of the underlying field by an
identity or a widening conversion, the method throws an
IllegalArgumentException.
Sets the value of the field represented by thispublic void setFloat(Object obj, float f)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object argument to the specified float value. See Field.set for the detailed
procedure.
If the new value cannot be converted to the type of the underlying field by an
identity or a widening conversion, the method throws an
IllegalArgumentException.
Sets the value of the field represented by thispublic void setDouble(Object obj, double d)throws NullPointerException, IllegalArgumentException,IllegalAccessException
Field object on the specified
object argument to the specified double value. See Field.set for the detailed
procedure.
If the underlying field is not of type double, the method throws an
IllegalArgumentException.