Module java.base

Class Field

All Implemented Interfaces:
AnnotatedElement, Member

public final class Field
extends AccessibleObject
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.

Since:
1.1
See Also:
Member, Class, Class.getFields(), Class.getField(String), Class.getDeclaredFields(), Class.getDeclaredField(String)
  • Field Summary

    Fields declared in interface java.lang.reflect.Member

    DECLARED, PUBLIC
  • Method Summary

    Modifier and Type Method 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>
    T
    getAnnotation​(Class<T> annotationClass)
    Returns this element's annotation for the specified type if such an annotation is present, else null.
    <T extends Annotation>
    T[]
    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.
    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 setAccessible​(boolean flag)
    Set the accessible flag for this reflected object to the indicated boolean 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.

    Methods declared in class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait
  • Method Details

    • setAccessible

      public void setAccessible​(boolean flag)
      Description copied from class: AccessibleObject
      Set the accessible flag for this reflected object to the indicated boolean value. A value of true indicates that the reflected object should suppress checks for Java language access control when it is used. A value of false indicates that the reflected object should enforce checks for Java language access control when it is used, with the variation noted in the class description.

      This method may be used by a caller in class C to enable access to a member of declaring class D if any of the following hold:

      • C and D are in the same module.
      • The member is public and D is public in a package that the module containing D exports to at least the module containing C.
      • The member is protected static, D is public in a package that the module containing D exports to at least the module containing C, and C is a subclass of D.
      • D is in a package that the module containing D opens to at least the module containing C. All packages in unnamed and open modules are open to all modules and so this method always succeeds when D is in an unnamed or open module.

      This method cannot be used to enable access to private members, members with default (package) access, protected instance members, or protected constructors when the declaring class is in a different module to the caller and the package containing the declaring class is not open to the caller's module.

      This method cannot be used to enable write access to a non-modifiable final field. The following fields are non-modifiable:

      • static final fields declared in any class or interface
      • final fields declared in a hidden class
      • final fields declared in a record

      The accessible flag when true suppresses Java language access control checks to only enable read access to these non-modifiable final fields.

      If there is a security manager, its checkPermission method is first called with a ReflectPermission("suppressAccessChecks") permission.

      Overrides:
      setAccessible in class AccessibleObject
      Parameters:
      flag - the new value for the accessible flag
      Throws:
      InaccessibleObjectException - if access cannot be enabled
      SecurityException - if the request is denied by the security manager
      See Also:
      AccessibleObject.trySetAccessible(), MethodHandles.privateLookupIn(java.lang.Class<?>, java.lang.invoke.MethodHandles.Lookup)
    • getDeclaringClass

      public Class<?> getDeclaringClass()
      Returns the Class object representing the class or interface that declares the field represented by this Field object.
      Specified by:
      getDeclaringClass in interface Member
      Returns:
      an object representing the declaring class of the underlying member
    • getName

      public String getName()
      Returns the name of the field represented by this Field object.
      Specified by:
      getName in interface Member
      Returns:
      the simple name of the underlying member
    • getModifiers

      public 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.
      Specified by:
      getModifiers in interface Member
      Returns:
      the Java language modifiers for the underlying member
      See Also:
      Modifier
    • isEnumConstant

      public boolean isEnumConstant()
      Returns true if this field represents an element of an enumerated type; returns false otherwise.
      Returns:
      true if and only if this field represents an element of an enumerated type.
      Since:
      1.5
    • isSynthetic

      public boolean isSynthetic()
      Returns true if this field is a synthetic field; returns false otherwise.
      Specified by:
      isSynthetic in interface Member
      Returns:
      true if and only if this field is a synthetic field as defined by the Java Language Specification.
      Since:
      1.5
    • getType

      public Class<?> getType()
      Returns a Class object that identifies the declared type for the field represented by this Field object.
      Returns:
      a Class object identifying the declared type of the field represented by this object
    • getGenericType

      public Type getGenericType()
      Returns a Type object that represents the declared type for the field represented by this Field object.

      If the declared type of the field is a parameterized type, the Type object returned must accurately reflect the actual type arguments 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.

      Returns:
      a Type object that represents the declared type for the field represented by this Field object
      Throws:
      GenericSignatureFormatError - if the generic field signature does not conform to the format specified in The Java™ Virtual Machine Specification
      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
      Since:
      1.5
    • equals

      public boolean equals​(Object obj)
      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.
      Overrides:
      equals in class Object
      Parameters:
      obj - the reference object with which to compare.
      Returns:
      true if this object is the same as the obj argument; false otherwise.
      See Also:
      Object.hashCode(), HashMap
    • 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
      Returns:
      a hash code value for this object.
      See Also:
      Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)
    • toString

      public String toString()
      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.

      Overrides:
      toString in class Object
      Returns:
      a string describing this Field
      See Java Language Specification:
      8.3.1 Field Modifiers
    • toGenericString

      public String toGenericString()
      Returns a string describing this 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.

      Returns:
      a string describing this Field, including its generic type
      See Java Language Specification:
      8.3.1 Field Modifiers
      Since:
      1.5
    • get

      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 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.

      Parameters:
      obj - object from which the represented field's value is to be extracted
      Returns:
      the value of the represented field in object obj; primitive values are wrapped in an appropriate object before being returned
      Throws:
      IllegalAccessException - 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.
    • getBoolean

      public boolean getBoolean​(Object obj) throws IllegalArgumentException, IllegalAccessException
      Gets the value of a static or instance boolean field.
      Parameters:
      obj - the object to extract the boolean value from
      Returns:
      the value of the boolean field
      Throws:
      IllegalAccessException - 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.
      See Also:
      get(java.lang.Object)
    • getByte

      public byte getByte​(Object obj) throws IllegalArgumentException, IllegalAccessException
      Gets the value of a static or instance byte field.
      Parameters:
      obj - the object to extract the byte value from
      Returns:
      the value of the byte field
      Throws:
      IllegalAccessException - 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.
      See Also:
      get(java.lang.Object)
    • getChar

      public char getChar​(Object obj) throws IllegalArgumentException, IllegalAccessException
      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 value from
      Returns:
      the value of the field converted to type char
      Throws:
      IllegalAccessException - 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.
      See Also:
      get(java.lang.Object)
    • getShort

      public short getShort​(Object obj) throws IllegalArgumentException, IllegalAccessException
      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 value from
      Returns:
      the value of the field converted to type short
      Throws:
      IllegalAccessException - 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.
      See Also:
      get(java.lang.Object)
    • getInt

      public int getInt​(Object obj) throws IllegalArgumentException, IllegalAccessException
      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 value from
      Returns:
      the value of the field converted to type int
      Throws:
      IllegalAccessException - 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.
      See Also:
      get(java.lang.Object)
    • getLong

      public long getLong​(Object obj) throws IllegalArgumentException, IllegalAccessException
      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 value from
      Returns:
      the value of the field converted to type long
      Throws:
      IllegalAccessException - 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.
      See Also:
      get(java.lang.Object)
    • getFloat

      public float getFloat​(Object obj) throws IllegalArgumentException, IllegalAccessException
      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 value from
      Returns:
      the value of the field converted to type float
      Throws:
      IllegalAccessException - 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.
      See Also:
      get(java.lang.Object)
    • getDouble

      public double getDouble​(Object obj) throws IllegalArgumentException, IllegalAccessException
      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 value from
      Returns:
      the value of the field converted to type double
      Throws:
      IllegalAccessException - 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.
      See Also:
      get(java.lang.Object)
    • set

      public 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 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, this Field object has write access if and only if the following conditions are met:

      If any of the above checks is not met, this method throws an IllegalAccessException.

      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.

      Parameters:
      obj - the object whose field should be modified
      value - the new value for the field of obj being modified
      Throws:
      IllegalAccessException - if this Field object is enforcing Java language access control and the underlying field is inaccessible or final; or if this Field object has no write access.
      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.
    • setBoolean

      public void setBoolean​(Object obj, boolean z) throws IllegalArgumentException, IllegalAccessException
      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
      z - the new value for the field of obj being modified
      Throws:
      IllegalAccessException - if this Field object is enforcing Java language access control and the underlying field is either inaccessible or final; or if this Field object has no write access.
      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.
      See Also:
      set(java.lang.Object, java.lang.Object)
    • setByte

      public void setByte​(Object obj, byte b) throws IllegalArgumentException, IllegalAccessException
      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
      b - the new value for the field of obj being modified
      Throws:
      IllegalAccessException - if this Field object is enforcing Java language access control and the underlying field is either inaccessible or final; or if this Field object has no write access.
      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.
      See Also:
      set(java.lang.Object, java.lang.Object)
    • setChar

      public void setChar​(Object obj, char c) throws IllegalArgumentException, IllegalAccessException
      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
      c - the new value for the field of obj being modified
      Throws:
      IllegalAccessException - if this Field object is enforcing Java language access control and the underlying field is either inaccessible or final; or if this Field object has no write access.
      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.
      See Also:
      set(java.lang.Object, java.lang.Object)
    • setShort

      public void setShort​(Object obj, short s) throws IllegalArgumentException, IllegalAccessException
      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
      s - the new value for the field of obj being modified
      Throws:
      IllegalAccessException - if this Field object is enforcing Java language access control and the underlying field is either inaccessible or final; or if this Field object has no write access.
      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.
      See Also:
      set(java.lang.Object, java.lang.Object)
    • setInt

      public void setInt​(Object obj, int i) throws IllegalArgumentException, IllegalAccessException
      Sets the value of a field as an int on the specified object. This method is equivalent to set(obj, iObj), where iObj is an Integer object and iObj.intValue() == i.
      Parameters:
      obj - the object whose field should be modified
      i - the new value for the field of obj being modified
      Throws:
      IllegalAccessException - if this Field object is enforcing Java language access control and the underlying field is either inaccessible or final; or if this Field object has no write access.
      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.
      See Also:
      set(java.lang.Object, java.lang.Object)
    • setLong

      public void setLong​(Object obj, long l) throws IllegalArgumentException, IllegalAccessException
      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
      l - the new value for the field of obj being modified
      Throws:
      IllegalAccessException - if this Field object is enforcing Java language access control and the underlying field is either inaccessible or final; or if this Field object has no write access.
      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.
      See Also:
      set(java.lang.Object, java.lang.Object)
    • setFloat

      public void setFloat​(Object obj, float f) throws IllegalArgumentException, IllegalAccessException
      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
      f - the new value for the field of obj being modified
      Throws:
      IllegalAccessException - if this Field object is enforcing Java language access control and the underlying field is either inaccessible or final; or if this Field object has no write access.
      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.
      See Also:
      set(java.lang.Object, java.lang.Object)
    • setDouble

      public void setDouble​(Object obj, double d) throws IllegalArgumentException, IllegalAccessException
      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
      d - the new value for the field of obj being modified
      Throws:
      IllegalAccessException - if this Field object is enforcing Java language access control and the underlying field is either inaccessible or final; or if this Field object has no write access.
      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.
      See Also:
      set(java.lang.Object, java.lang.Object)
    • getAnnotation

      public <T extends Annotation> T getAnnotation​(Class<T> annotationClass)
      Returns this element's annotation for the specified type if such an annotation is present, else null.

      Note that any annotation returned by this method is a declaration annotation.

      Specified by:
      getAnnotation in interface AnnotatedElement
      Overrides:
      getAnnotation in class AccessibleObject
      Type Parameters:
      T - the type of the annotation to query for and return if present
      Parameters:
      annotationClass - the Class object corresponding to the annotation type
      Returns:
      this element's annotation for the specified annotation type if present on this element, else null
      Throws:
      NullPointerException - if the given annotation class is null
      Since:
      1.5
    • getAnnotationsByType

      public <T extends Annotation> T[] getAnnotationsByType​(Class<T> annotationClass)
      Returns annotations that are associated with this element. If there are no annotations associated with this element, the return value is an array of length 0. The difference between this method and 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.

      Note that any annotations returned by this method are declaration annotations.

      Specified by:
      getAnnotationsByType in interface AnnotatedElement
      Overrides:
      getAnnotationsByType in class AccessibleObject
      Type Parameters:
      T - the type of the annotation to query for and return if present
      Parameters:
      annotationClass - the Class object corresponding to the annotation type
      Returns:
      all this element's annotations for the specified annotation type if associated with this element, else an array of length zero
      Throws:
      NullPointerException - if the given annotation class is null
      Since:
      1.8
    • getAnnotatedType

      public 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.
      Returns:
      an object representing the declared type of the field represented by this Field
      Since:
      1.8