Package java.lang.reflect

Class Field

  • All Implemented Interfaces:
    AnnotatedElement, Member
    public final class Field
extends AccessibleObject
implements Member
    This class represents a field. Information about the field can be accessed, and the field's value can be accessed dynamically.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean equals​(Object other)
      Returns true if other has the same declaring class, name and type as this field.
      Object get​(Object object)
      Returns the value of the field in the specified object.
      <A extends Annotation>
      A      		 getAnnotation​(Class<A> annotationType)
      Returns, for this element, the annotation with the specified type, or null if no annotation with the specified type is present (including inherited annotations).
      boolean getBoolean​(Object object)
      Returns the value of the field in the specified object as a boolean.
      byte getByte​(Object object)
      Returns the value of the field in the specified object as a byte.
      char getChar​(Object object)
      Returns the value of the field in the specified object as a char.
      Annotation[] getDeclaredAnnotations()
      Returns, for this element, all annotations that are explicitly declared (not inherited).
      Class<?> getDeclaringClass()
      Returns the class that declares this member.
      int getDexFieldIndex()
      Returns the index of this field's ID in its dex file.
      double getDouble​(Object object)
      Returns the value of the field in the specified object as a double.
      float getFloat​(Object object)
      Returns the value of the field in the specified object as a float .
      Type getGenericType()
      Returns the generic type of this field.
      int getInt​(Object object)
      Returns the value of the field in the specified object as an int.
      long getLong​(Object object)
      Returns the value of the field in the specified object as a long.
      int getModifiers()
      Returns the modifiers for this field.
      String getName()
      Returns the name of this field.
      int getOffset()
      Returns the offset of the field within an instance, or for static fields, the class.
      short getShort​(Object object)
      Returns the value of the field in the specified object as a short .
      Class<?> getType()
      Return the Class associated with the type of this field.
      int hashCode()
      Returns an integer hash code for this object.
      boolean isAnnotationPresent​(Class<? extends Annotation> annotationType)
      Indicates whether or not this element has an annotation with the specified annotation type (including inherited annotations).
      boolean isEnumConstant()
      Indicates whether or not this field is an enumeration constant.
      boolean isSynthetic()
      Indicates whether or not this field is synthetic.
      void set​(Object object, Object value)
      Sets the value of the field in the specified object to the value.
      void setBoolean​(Object object, boolean value)
      Sets the value of the field in the specified object to the boolean value.
      void setByte​(Object object, byte value)
      Sets the value of the field in the specified object to the byte value.
      void setChar​(Object object, char value)
      Sets the value of the field in the specified object to the char value.
      void setDouble​(Object object, double value)
      Sets the value of the field in the specified object to the double value.
      void setFloat​(Object object, float value)
      Sets the value of the field in the specified object to the float value.
      void setInt​(Object object, int value)
      Set the value of the field in the specified object to the int value.
      void setLong​(Object object, long value)
      Sets the value of the field in the specified object to the long value.
      void setShort​(Object object, short value)
      Sets the value of the field in the specified object to the short value.
      String toGenericString()
      Returns the string representation of this field, including the field's generic type.
      String toString()
      Returns a string containing a concise, human-readable description of this field.

    • Field Detail

      • ORDER_BY_NAME_AND_DECLARING_CLASS

        public static final Comparator<Field> ORDER_BY_NAME_AND_DECLARING_CLASS
        Orders fields by their name and declaring class.

    • Method Detail

      • getModifiers

        public int getModifiers()
        Returns the modifiers for this field. The Modifier class should be used to decode the result.
        Specified by:
        getModifiers in interface Member
        Returns:
        the modifiers for this field
        See Also:
        Modifier

      • isEnumConstant

        public boolean isEnumConstant()
        Indicates whether or not this field is an enumeration constant.
        Returns:
        true if this field is an enumeration constant, false otherwise

      • isSynthetic

        public boolean isSynthetic()
        Indicates whether or not this field is synthetic.
        Specified by:
        isSynthetic in interface Member
        Returns:
        true if this field is synthetic, false otherwise

      • getName

        public String getName()
        Returns the name of this field.
        Specified by:
        getName in interface Member
        Returns:
        the name of this field

      • getDeclaringClass

        public Class<?> getDeclaringClass()
        Description copied from interface: Member
        Returns the class that declares this member.
        Specified by:
        getDeclaringClass in interface Member
        Returns:
        the declaring class

      • getType

        public Class<?> getType()
        Return the Class associated with the type of this field.
        Returns:
        the type of this field

      • getDexFieldIndex

        public int getDexFieldIndex()
        Returns the index of this field's ID in its dex file.

      • getOffset

        public int getOffset()
        Returns the offset of the field within an instance, or for static fields, the class.

      • hashCode

        public int hashCode()
        Returns an integer hash code for this object. By contract, any two objects for which Object.equals(java.lang.Object) returns true must return the same hash code value. This means that subclasses of Object usually override both methods or neither method.

        Note that hash values must not change over time unless information used in equals comparisons also changes.

        See Writing a correct hashCode method if you intend implementing your own hashCode method.

        Equivalent to getDeclaringClass().getName().hashCode() ^ getName().hashCode().

        Overrides:
        hashCode in class Object
        Returns:
        this object's hash code.
        See Also:
        Object.equals(java.lang.Object)

      • equals

        public boolean equals​(Object other)
        Returns true if other has the same declaring class, name and type as this field.
        Overrides:
        equals in class Object
        Parameters:
        other - the object to compare this instance with.
        Returns:
        true if the specified object is equal to this Object; false otherwise.
        See Also:
        Object.hashCode()

      • toGenericString

        public String toGenericString()
        Returns the string representation of this field, including the field's generic type.
        Returns:
        the string representation of this field

      • getAnnotation

        public <A extends Annotation> A getAnnotation​(Class<A> annotationType)
        Description copied from interface: AnnotatedElement
        Returns, for this element, the annotation with the specified type, or null if no annotation with the specified type is present (including inherited annotations).
        Specified by:
        getAnnotation in interface AnnotatedElement
        Overrides:
        getAnnotation in class AccessibleObject
        Parameters:
        annotationType - the type of the annotation to search for
        Returns:
        the annotation with the specified type or null

      • isAnnotationPresent

        public boolean isAnnotationPresent​(Class<? extends Annotation> annotationType)
        Description copied from interface: AnnotatedElement
        Indicates whether or not this element has an annotation with the specified annotation type (including inherited annotations).
        Specified by:
        isAnnotationPresent in interface AnnotatedElement
        Overrides:
        isAnnotationPresent in class AccessibleObject
        Parameters:
        annotationType - the type of the annotation to search for
        Returns:
        true if the annotation exists, false otherwise

      • get

        public Object get​(Object object)
           throws IllegalAccessException,
                  IllegalArgumentException
        Returns the value of the field in the specified object. This reproduces the effect of object.fieldName

        If the type of this field is a primitive type, the field value is automatically boxed.

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        Parameters:
        object - the object to access
        Returns:
        the field value, possibly boxed
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • getBoolean

        public boolean getBoolean​(Object object)
                   throws IllegalAccessException,
                          IllegalArgumentException
        Returns the value of the field in the specified object as a boolean. This reproduces the effect of object.fieldName

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        Parameters:
        object - the object to access
        Returns:
        the field value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • getByte

        public byte getByte​(Object object)
             throws IllegalAccessException,
                    IllegalArgumentException
        Returns the value of the field in the specified object as a byte. This reproduces the effect of object.fieldName

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        Parameters:
        object - the object to access
        Returns:
        the field value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • getChar

        public char getChar​(Object object)
             throws IllegalAccessException,
                    IllegalArgumentException
        Returns the value of the field in the specified object as a char. This reproduces the effect of object.fieldName

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        Parameters:
        object - the object to access
        Returns:
        the field value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • getDouble

        public double getDouble​(Object object)
                 throws IllegalAccessException,
                        IllegalArgumentException
        Returns the value of the field in the specified object as a double. This reproduces the effect of object.fieldName

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        Parameters:
        object - the object to access
        Returns:
        the field value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • getFloat

        public float getFloat​(Object object)
               throws IllegalAccessException,
                      IllegalArgumentException
        Returns the value of the field in the specified object as a float . This reproduces the effect of object.fieldName

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        Parameters:
        object - the object to access
        Returns:
        the field value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • getInt

        public int getInt​(Object object)
           throws IllegalAccessException,
                  IllegalArgumentException
        Returns the value of the field in the specified object as an int. This reproduces the effect of object.fieldName

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        Parameters:
        object - the object to access
        Returns:
        the field value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • getLong

        public long getLong​(Object object)
             throws IllegalAccessException,
                    IllegalArgumentException
        Returns the value of the field in the specified object as a long. This reproduces the effect of object.fieldName

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        Parameters:
        object - the object to access
        Returns:
        the field value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • getShort

        public short getShort​(Object object)
               throws IllegalAccessException,
                      IllegalArgumentException
        Returns the value of the field in the specified object as a short . This reproduces the effect of object.fieldName

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        Parameters:
        object - the object to access
        Returns:
        the field value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • set

        public void set​(Object object,
                Object value)
         throws IllegalAccessException,
                IllegalArgumentException
        Sets the value of the field in the specified object to the value. This reproduces the effect of object.fieldName = value

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        If the field type is a primitive type, the value is automatically unboxed. If the unboxing fails, an IllegalArgumentException is thrown. If the value cannot be converted to the field type via a widening conversion, an IllegalArgumentException is thrown.

        Parameters:
        object - the object to access
        value - the new value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • setBoolean

        public void setBoolean​(Object object,
                       boolean value)
                throws IllegalAccessException,
                       IllegalArgumentException
        Sets the value of the field in the specified object to the boolean value. This reproduces the effect of object.fieldName = value

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        If the value cannot be converted to the field type via a widening conversion, an IllegalArgumentException is thrown.

        Parameters:
        object - the object to access
        value - the new value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • setByte

        public void setByte​(Object object,
                    byte value)
             throws IllegalAccessException,
                    IllegalArgumentException
        Sets the value of the field in the specified object to the byte value. This reproduces the effect of object.fieldName = value

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        If the value cannot be converted to the field type via a widening conversion, an IllegalArgumentException is thrown.

        Parameters:
        object - the object to access
        value - the new value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • setChar

        public void setChar​(Object object,
                    char value)
             throws IllegalAccessException,
                    IllegalArgumentException
        Sets the value of the field in the specified object to the char value. This reproduces the effect of object.fieldName = value

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        If the value cannot be converted to the field type via a widening conversion, an IllegalArgumentException is thrown.

        Parameters:
        object - the object to access
        value - the new value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • setDouble

        public void setDouble​(Object object,
                      double value)
               throws IllegalAccessException,
                      IllegalArgumentException
        Sets the value of the field in the specified object to the double value. This reproduces the effect of object.fieldName = value

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        If the value cannot be converted to the field type via a widening conversion, an IllegalArgumentException is thrown.

        Parameters:
        object - the object to access
        value - the new value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • setFloat

        public void setFloat​(Object object,
                     float value)
              throws IllegalAccessException,
                     IllegalArgumentException
        Sets the value of the field in the specified object to the float value. This reproduces the effect of object.fieldName = value

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        If the value cannot be converted to the field type via a widening conversion, an IllegalArgumentException is thrown.

        Parameters:
        object - the object to access
        value - the new value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • setInt

        public void setInt​(Object object,
                   int value)
            throws IllegalAccessException,
                   IllegalArgumentException
        Set the value of the field in the specified object to the int value. This reproduces the effect of object.fieldName = value

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        If the value cannot be converted to the field type via a widening conversion, an IllegalArgumentException is thrown.

        Parameters:
        object - the object to access
        value - the new value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • setLong

        public void setLong​(Object object,
                    long value)
             throws IllegalAccessException,
                    IllegalArgumentException
        Sets the value of the field in the specified object to the long value. This reproduces the effect of object.fieldName = value

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        If the value cannot be converted to the field type via a widening conversion, an IllegalArgumentException is thrown.

        Parameters:
        object - the object to access
        value - the new value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • setShort

        public void setShort​(Object object,
                     short value)
              throws IllegalAccessException,
                     IllegalArgumentException
        Sets the value of the field in the specified object to the short value. This reproduces the effect of object.fieldName = value

        If this field is static, the object argument is ignored. Otherwise, if the object is null, a NullPointerException is thrown. If the object is not an instance of the declaring class of the method, an IllegalArgumentException is thrown.

        If this Field object is enforcing access control (see AccessibleObject) and this field is not accessible from the current context, an IllegalAccessException is thrown.

        If the value cannot be converted to the field type via a widening conversion, an IllegalArgumentException is thrown.

        Parameters:
        object - the object to access
        value - the new value
        Throws:
        NullPointerException - if the object is null and the field is non-static
        IllegalArgumentException - if the object is not compatible with the declaring class
        IllegalAccessException - if this field is not accessible

      • toString

        public String toString()
        Returns a string containing a concise, human-readable description of this field.

        The format of the string is:

        1. modifiers (if any)
        2. type
        3. declaring class name
        4. '.'
        5. field name

        For example: public static java.io.InputStream java.lang.System.in

        Overrides:
        toString in class Object
        Returns:
        a printable representation for this field