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Java Source Code / Java Documentation » 6.0 JDK Modules » j2me » java.lang.reflect 
Source Cross Reference  Class Diagram Java Document (Java Doc) 


java.lang.Object
   java.lang.reflect.AccessibleObject
      java.lang.reflect.Field

Field
final public class Field extends AccessibleObject implements Member(Code)
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
See Also:   java.lang.Class
See Also:   java.lang.Class.getFields
See Also:   java.lang.Class.getField(String)
See Also:   java.lang.Class.getDeclaredFields
See Also:   java.lang.Class.getDeclaredField(String)
author:
   Nakul Saraiya





Method Summary
public  booleanequals(Object obj)
     Compares this Field against the specified object.
native public  Objectget(Object obj)
     Returns the value of the field represented by this Field, on the specified object.
native public  booleangetBoolean(Object obj)
     Gets the value of a static or instance boolean field.
native public  bytegetByte(Object obj)
     Gets the value of a static or instance byte field.
native public  chargetChar(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.
public  ClassgetDeclaringClass()
     Returns the Class object representing the class or interface that declares the field represented by this Field object.
native public  doublegetDouble(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.
native public  floatgetFloat(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.
native public  intgetInt(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.
native public  longgetLong(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.
public  intgetModifiers()
     Returns the Java language modifiers for the field represented by this Field object, as an integer.
public  StringgetName()
     Returns the name of the field represented by this Field object.
native public  shortgetShort(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.
public  ClassgetType()
     Returns a Class object that identifies the declared type for the field represented by this Field object.
static  StringgetTypeName(Class type)
    
public  inthashCode()
     Returns a hashcode for this Field.
native public  voidset(Object obj, Object value)
     Sets the field represented by this Field object on the specified object argument to the specified new value.
native public  voidsetBoolean(Object obj, boolean z)
     Sets the value of a field as a boolean on the specified object.
native public  voidsetByte(Object obj, byte b)
     Sets the value of a field as a byte on the specified object.
native public  voidsetChar(Object obj, char c)
     Sets the value of a field as a char on the specified object.
native public  voidsetDouble(Object obj, double d)
     Sets the value of a field as a double on the specified object.
native public  voidsetFloat(Object obj, float f)
     Sets the value of a field as a float on the specified object.
native public  voidsetInt(Object obj, int i)
     Sets the value of a field as an int on the specified object.
native public  voidsetLong(Object obj, long l)
     Sets the value of a field as a long on the specified object.
native public  voidsetShort(Object obj, short s)
     Sets the value of a field as a short on the specified object.
public  StringtoString()
     Returns a string describing this Field.



Method Detail
equals
public boolean equals(Object obj)(Code)
Compares this 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.



get
native public Object get(Object obj) throws IllegalArgumentException, IllegalAccessException(Code)
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 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.
Parameters:
  obj - object from which the represented field's value isto be extracted the value of the represented field in objectobj; primitive values are wrapped in an appropriateobject before being returned
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof).
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.




getBoolean
native public boolean getBoolean(Object obj) throws IllegalArgumentException, IllegalAccessException(Code)
Gets the value of a static or instance boolean field.
Parameters:
  obj - the object to extract the boolean valuefrom the value of the boolean field
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not an instance of the class or interface declaring theunderlying field (or a subclass or implementor thereof), or if the field value cannot beconverted to the type boolean by a widening conversion.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.get



getByte
native public byte getByte(Object obj) throws IllegalArgumentException, IllegalAccessException(Code)
Gets the value of a static or instance byte field.
Parameters:
  obj - the object to extract the byte valuefrom the value of the byte field
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not an instance of the class or interface declaring theunderlying field (or a subclass or implementor thereof), or if the field value cannot beconverted to the type byte by a widening conversion.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.get



getChar
native public char getChar(Object obj) throws IllegalArgumentException, IllegalAccessException(Code)
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.
Parameters:
  obj - the object to extract the char valuefrom the value of the field converted to type char
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not an instance of the class or interface declaring theunderlying field (or a subclass or implementor thereof), or if the field value cannot beconverted to the type char by a widening conversion.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.get



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



getDouble
native public double getDouble(Object obj) throws IllegalArgumentException, IllegalAccessException(Code)
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.
Parameters:
  obj - the object to extract the double valuefrom the value of the field converted to type double
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not an instance of the class or interface declaring theunderlying field (or a subclass or implementor thereof), or if the field value cannot beconverted to the type double by a widening conversion.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.get



getFloat
native public float getFloat(Object obj) throws IllegalArgumentException, IllegalAccessException(Code)
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.
Parameters:
  obj - the object to extract the float valuefrom the value of the field converted to type float
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not an instance of the class or interface declaring theunderlying field (or a subclass or implementor thereof), or if the field value cannot beconverted to the type float by a widening conversion.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.get



getInt
native public int getInt(Object obj) throws IllegalArgumentException, IllegalAccessException(Code)
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.
Parameters:
  obj - the object to extract the int valuefrom the value of the field converted to type int
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not an instance of the class or interface declaring theunderlying field (or a subclass or implementor thereof), or if the field value cannot beconverted to the type int by a widening conversion.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.get



getLong
native public long getLong(Object obj) throws IllegalArgumentException, IllegalAccessException(Code)
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.
Parameters:
  obj - the object to extract the long valuefrom the value of the field converted to type long
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not an instance of the class or interface declaring theunderlying field (or a subclass or implementor thereof), or if the field value cannot beconverted to the type long by a widening conversion.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.get



getModifiers
public int getModifiers()(Code)
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



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



getShort
native public short getShort(Object obj) throws IllegalArgumentException, IllegalAccessException(Code)
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.
Parameters:
  obj - the object to extract the short valuefrom the value of the field converted to type short
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not an instance of the class or interface declaring theunderlying field (or a subclass or implementor thereof), or if the field value cannot beconverted to the type short by a widening conversion.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.get



getType
public Class getType()(Code)
Returns a Class object that identifies the declared type for the field represented by this Field object. a Class object identifying the declaredtype of the field represented by this object



getTypeName
static String getTypeName(Class type)(Code)



hashCode
public int hashCode()(Code)
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.



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

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.
Parameters:
  obj - the object whose field should be modified
Parameters:
  value - the new value for the field of objbeing modified
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof), or if an unwrapping conversion fails.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.




setBoolean
native public void setBoolean(Object obj, boolean z) throws IllegalArgumentException, IllegalAccessException(Code)
Sets the value of a field as a boolean on the specified object. This method is equivalent to set(obj, zObj), where zObj is a Boolean object and zObj.booleanValue() == z.
Parameters:
  obj - the object whose field should be modified
Parameters:
  z - the new value for the field of objbeing modified
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof), or if an unwrapping conversion fails.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.set



setByte
native public void setByte(Object obj, byte b) throws IllegalArgumentException, IllegalAccessException(Code)
Sets the value of a field as a byte on the specified object. This method is equivalent to set(obj, bObj), where bObj is a Byte object and bObj.byteValue() == b.
Parameters:
  obj - the object whose field should be modified
Parameters:
  b - the new value for the field of objbeing modified
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof), or if an unwrapping conversion fails.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.set



setChar
native public void setChar(Object obj, char c) throws IllegalArgumentException, IllegalAccessException(Code)
Sets the value of a field as a char on the specified object. This method is equivalent to set(obj, cObj), where cObj is a Character object and cObj.charValue() == c.
Parameters:
  obj - the object whose field should be modified
Parameters:
  c - the new value for the field of objbeing modified
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof), or if an unwrapping conversion fails.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.set



setDouble
native public void setDouble(Object obj, double d) throws IllegalArgumentException, IllegalAccessException(Code)
Sets the value of a field as a double on the specified object. This method is equivalent to set(obj, dObj), where dObj is a Double object and dObj.doubleValue() == d.
Parameters:
  obj - the object whose field should be modified
Parameters:
  d - the new value for the field of objbeing modified
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof), or if an unwrapping conversion fails.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.set



setFloat
native public void setFloat(Object obj, float f) throws IllegalArgumentException, IllegalAccessException(Code)
Sets the value of a field as a float on the specified object. This method is equivalent to set(obj, fObj), where fObj is a Float object and fObj.floatValue() == f.
Parameters:
  obj - the object whose field should be modified
Parameters:
  f - the new value for the field of objbeing modified
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof), or if an unwrapping conversion fails.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.set



setInt
native public void setInt(Object obj, int i) throws IllegalArgumentException, IllegalAccessException(Code)
Sets the value of a field as an int on the specified object. This method is equivalent to set(obj, iObj), where iObj is a Integer object and iObj.intValue() == i.
Parameters:
  obj - the object whose field should be modified
Parameters:
  i - the new value for the field of objbeing modified
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof), or if an unwrapping conversion fails.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.set



setLong
native public void setLong(Object obj, long l) throws IllegalArgumentException, IllegalAccessException(Code)
Sets the value of a field as a long on the specified object. This method is equivalent to set(obj, lObj), where lObj is a Long object and lObj.longValue() == l.
Parameters:
  obj - the object whose field should be modified
Parameters:
  l - the new value for the field of objbeing modified
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof), or if an unwrapping conversion fails.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.set



setShort
native public void setShort(Object obj, short s) throws IllegalArgumentException, IllegalAccessException(Code)
Sets the value of a field as a short on the specified object. This method is equivalent to set(obj, sObj), where sObj is a Short object and sObj.shortValue() == s.
Parameters:
  obj - the object whose field should be modified
Parameters:
  s - the new value for the field of objbeing modified
exception:
  IllegalAccessException - if the underlying fieldis inaccessible.
exception:
  IllegalArgumentException - if the specified object is not aninstance of the class or interface declaring the underlyingfield (or a subclass or implementor thereof), or if an unwrapping conversion fails.
exception:
  NullPointerException - if the specified object is nulland the field is an instance field.
exception:
  ExceptionInInitializerError - if the initialization provokedby this method fails.
See Also:   Field.set



toString
public String toString()(Code)
Returns 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.




Methods inherited from java.lang.reflect.AccessibleObject
public boolean isAccessible()(Code)(Java Doc)
public static void setAccessible(AccessibleObject[] array, boolean flag) throws SecurityException(Code)(Java Doc)
public void setAccessible(boolean flag) throws SecurityException(Code)(Java Doc)

Methods inherited from java.lang.Object
public boolean equals(Object obj)(Code)(Java Doc)
final native public Class getClass()(Code)(Java Doc)
native public int hashCode()(Code)(Java Doc)
final native public void notify()(Code)(Java Doc)
final native public void notifyAll()(Code)(Java Doc)
public String toString()(Code)(Java Doc)
final native public void wait(long timeout) throws InterruptedException(Code)(Java Doc)
final public void wait(long timeout, int nanos) throws InterruptedException(Code)(Java Doc)
final public void wait() throws InterruptedException(Code)(Java Doc)

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