# Class BasicAttribute

java.lang.Object
javax.naming.directory.BasicAttribute

All Implemented Interfaces:
  `Serializable, Cloneable, Attribute`

public class BasicAttribute extends Object implements Attribute
This class provides a basic implementation of the `Attribute` interface.

This implementation does not support the schema methods `getAttributeDefinition()` and `getAttributeSyntaxDefinition()`. They simply throw `OperationNotSupportedException`. Subclasses of `BasicAttribute` should override these methods if they support them.

The `BasicAttribute` class by default uses `Object.equals()` to determine equality of attribute values when testing for equality or when searching for values, except when the value is an array. For an array, each element of the array is checked using `Object.equals()`. Subclasses of `BasicAttribute` can make use of schema information when doing similar equality checks by overriding methods in which such use of schema is meaningful. Similarly, the `BasicAttribute` class by default returns the values passed to its constructor and/or manipulated using the add/remove methods. Subclasses of `BasicAttribute` can override `get()` and `getAll()` to get the values dynamically from the directory (or implement the `Attribute` interface directly instead of subclassing `BasicAttribute`).

Note that updates to `BasicAttribute` (such as adding or removing a value) does not affect the corresponding representation of the attribute in the directory. Updates to the directory can only be effected using operations in the `DirContext` interface.

A `BasicAttribute` instance is not synchronized against concurrent multithreaded access. Multiple threads trying to access and modify a `BasicAttribute` should lock the object.

Since:
  1.3
See Also:
  - Serialized Form

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected String`
  `attrID`
  Holds the attribute's id.
  `protected boolean`
  `ordered`
  A flag for recording whether this attribute's values are ordered.
  `protected Vector<Object>`
  `values`
  Holds the attribute's values.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `BasicAttribute(String id)`
  Constructs a new instance of an unordered attribute with no value.
  `BasicAttribute(String id, boolean ordered)`
  Constructs a new instance of a possibly ordered attribute with no value.
  `BasicAttribute(String id, Object value)`
  Constructs a new instance of an unordered attribute with a single value.
  `BasicAttribute(String id, Object value, boolean ordered)`
  Constructs a new instance of a possibly ordered attribute with a single value.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `add(int ix, Object attrVal)`
  Adds an attribute value to the ordered list of attribute values.
  `boolean`
  `add(Object attrVal)`
  Adds a new value to this attribute.
  `void`
  `clear()`
  Removes all values from this attribute.
  `Object`
  `clone()`
  Makes a copy of the attribute.
  `boolean`
  `contains(Object attrVal)`
  Determines whether a value is in this attribute.
  `boolean`
  `equals(Object obj)`
  Determines whether obj is equal to this attribute.
  `Object`
  `get()`
  Retrieves one of this attribute's values.
  `Object`
  `get(int ix)`
  Retrieves the attribute value from the ordered list of attribute values.
  `NamingEnumeration<?>`
  `getAll()`
  Retrieves an enumeration of this attribute's values.
  `DirContext`
  `getAttributeDefinition()`
  Retrieves this attribute's schema definition.
  `DirContext`
  `getAttributeSyntaxDefinition()`
  Retrieves the syntax definition associated with this attribute.
  `String`
  `getID()`
  Retrieves the id of this attribute.
  `int`
  `hashCode()`
  Calculates the hash code of this attribute.
  `boolean`
  `isOrdered()`
  Determines whether this attribute's values are ordered.
  `Object`
  `remove(int ix)`
  Removes an attribute value from the ordered list of attribute values.
  `boolean`
  `remove(Object attrval)`
  Removes a specified value from this attribute.
  `Object`
  `set(int ix, Object attrVal)`
  Sets an attribute value in the ordered list of attribute values.
  `int`
  `size()`
  Retrieves the number of values in this attribute.
  `String`
  `toString()`
  Generates the string representation of this attribute.

  ### Methods declared in class Object

  `finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Field Details

  - ### attrID

    protected String attrID
    Holds the attribute's id. It is initialized by the public constructor and cannot be null unless methods in BasicAttribute that use attrID have been overridden.

  - ### values

    protected transient Vector<Object> values
    Holds the attribute's values. Initialized by public constructors. Cannot be null unless methods in BasicAttribute that use values have been overridden.

  - ### ordered

    protected boolean ordered
    A flag for recording whether this attribute's values are ordered.

- ## Constructor Details

  - ### BasicAttribute

    public BasicAttribute(String id)
    Constructs a new instance of an unordered attribute with no value.
    Parameters:
      `id` - The attribute's id. It cannot be null.

  - ### BasicAttribute

    public BasicAttribute(String id, Object value)
    Constructs a new instance of an unordered attribute with a single value.
    Parameters:
      `id` - The attribute's id. It cannot be null.
      `value` - The attribute's value. If null, a null value is added to the attribute.

  - ### BasicAttribute

    public BasicAttribute(String id, boolean ordered)
    Constructs a new instance of a possibly ordered attribute with no value.
    Parameters:
      `id` - The attribute's id. It cannot be null.
      `ordered` - true means the attribute's values will be ordered; false otherwise.

  - ### BasicAttribute

    public BasicAttribute(String id, Object value, boolean ordered)
    Constructs a new instance of a possibly ordered attribute with a single value.
    Parameters:
      `id` - The attribute's id. It cannot be null.
      `value` - The attribute's value. If null, a null value is added to the attribute.
      `ordered` - true means the attribute's values will be ordered; false otherwise.

- ## Method Details

  - ### clone

    public Object clone()
    Description copied from interface: `Attribute`
    Makes a copy of the attribute. The copy contains the same attribute values as the original attribute: the attribute values are not themselves cloned. Changes to the copy will not affect the original and vice versa.
    Specified by:
      `clone` in interface `Attribute`
    Overrides:
      `clone` in class `Object`
    Returns:
      A non-null copy of the attribute.
    See Also:
      - `Cloneable`

  - ### equals

    public boolean equals(Object obj)
    Determines whether obj is equal to this attribute. Two attributes are equal if their attribute-ids, syntaxes and values are equal. If the attribute values are unordered, the order that the values were added are irrelevant. If the attribute values are ordered, then the order the values must match. If obj is null or not an Attribute, false is returned.

    By default `Object.equals()` is used when comparing the attribute id and its values except when a value is an array. For an array, each element of the array is checked using `Object.equals()`. A subclass may override this to make use of schema syntax information and matching rules, which define what it means for two attributes to be equal. How and whether a subclass makes use of the schema information is determined by the subclass. If a subclass overrides `equals()`, it should also override `hashCode()` such that two attributes that are equal have the same hash code.

    Overrides:
      `equals` in class `Object`
    Parameters:
      `obj` - The possibly null object to check.
    Returns:
      true if obj is equal to this attribute; false otherwise.
    See Also:
      - `hashCode()`
      - `contains(Object)`

  - ### hashCode

    public int hashCode()
    Calculates the hash code of this attribute.

    The hash code is computed by adding the hash code of the attribute's id and that of all of its values except for values that are arrays. For an array, the hash code of each element of the array is summed. If a subclass overrides `hashCode()`, it should override `equals()` as well so that two attributes that are equal have the same hash code.

    Overrides:
      `hashCode` in class `Object`
    Returns:
      an int representing the hash code of this attribute.
    See Also:
      - `equals(Object)`

  - ### toString

    public String toString()
    Generates the string representation of this attribute. The string consists of the attribute's id and its values. This string is meant for debugging and not meant to be interpreted programmatically.
    Overrides:
      `toString` in class `Object`
    Returns:
      The non-null string representation of this attribute.

  - ### getAll

    public NamingEnumeration<?> getAll() throws NamingException
    Retrieves an enumeration of this attribute's values.

    By default, the values returned are those passed to the constructor and/or manipulated using the add/replace/remove methods. A subclass may override this to retrieve the values dynamically from the directory.

    Specified by:
      `getAll` in interface `Attribute`
    Returns:
      A non-null enumeration of the attribute's values. Each element of the enumeration is a possibly null Object. The object's class is the class of the attribute value. The element is null if the attribute's value is null. If the attribute has zero values, an empty enumeration is returned.
    Throws:
      `NamingException` - If a naming exception was encountered while retrieving the values.
    See Also:
      - `Attribute.isOrdered()`

  - ### get

    public Object get() throws NamingException
    Retrieves one of this attribute's values.

    By default, the value returned is one of those passed to the constructor and/or manipulated using the add/replace/remove methods. A subclass may override this to retrieve the value dynamically from the directory.

    Specified by:
      `get` in interface `Attribute`
    Returns:
      A possibly null object representing one of the attribute's value. It is null if the attribute's value is null.
    Throws:
      `NamingException` - If a naming exception was encountered while retrieving the value.

  - ### size

    public int size()
    Description copied from interface: `Attribute`
    Retrieves the number of values in this attribute.
    Specified by:
      `size` in interface `Attribute`
    Returns:
      The nonnegative number of values in this attribute.

  - ### getID

    public String getID()
    Description copied from interface: `Attribute`
    Retrieves the id of this attribute.
    Specified by:
      `getID` in interface `Attribute`
    Returns:
      The id of this attribute. It cannot be null.

  - ### contains

    public boolean contains(Object attrVal)
    Determines whether a value is in this attribute.

    By default, `Object.equals()` is used when comparing `attrVal` with this attribute's values except when `attrVal` is an array. For an array, each element of the array is checked using `Object.equals()`. A subclass may use schema information to determine equality.

    Specified by:
      `contains` in interface `Attribute`
    Parameters:
      `attrVal` - The possibly null value to check. If null, check whether the attribute has an attribute value whose value is null.
    Returns:
      true if attrVal is one of this attribute's values; false otherwise.
    See Also:
      - `Object.equals(Object)`
      - `equals(Object)`

  - ### add

    public boolean add(Object attrVal)
    Adds a new value to this attribute.

    By default, `Object.equals()` is used when comparing `attrVal` with this attribute's values except when `attrVal` is an array. For an array, each element of the array is checked using `Object.equals()`. A subclass may use schema information to determine equality.

    Specified by:
      `add` in interface `Attribute`
    Parameters:
      `attrVal` - The new possibly null value to add. If null, null is added as an attribute value.
    Returns:
      true if a value was added; false otherwise.

  - ### remove

    public boolean remove(Object attrval)
    Removes a specified value from this attribute.

    By default, `Object.equals()` is used when comparing `attrVal` with this attribute's values except when `attrVal` is an array. For an array, each element of the array is checked using `Object.equals()`. A subclass may use schema information to determine equality.

    Specified by:
      `remove` in interface `Attribute`
    Parameters:
      `attrval` - The possibly null value to remove from this attribute. If null, remove the attribute value that is null.
    Returns:
      true if the value was removed; false otherwise.

  - ### clear

    public void clear()
    Description copied from interface: `Attribute`
    Removes all values from this attribute.
    Specified by:
      `clear` in interface `Attribute`

  - ### isOrdered

    public boolean isOrdered()
    Description copied from interface: `Attribute`
    Determines whether this attribute's values are ordered. If an attribute's values are ordered, duplicate values are allowed. If an attribute's values are unordered, they are presented in any order and there are no duplicate values.
    Specified by:
      `isOrdered` in interface `Attribute`
    Returns:
      true if this attribute's values are ordered; false otherwise.
    See Also:
      - `Attribute.get(int)`
      - `Attribute.remove(int)`
      - `Attribute.add(int, java.lang.Object)`
      - `Attribute.set(int, java.lang.Object)`

  - ### get

    public Object get(int ix) throws NamingException
    Description copied from interface: `Attribute`
    Retrieves the attribute value from the ordered list of attribute values. This method returns the value at the `ix` index of the list of attribute values. If the attribute values are unordered, this method returns the value that happens to be at that index.
    Specified by:
      `get` in interface `Attribute`
    Parameters:
      `ix` - The index of the value in the ordered list of attribute values. `0 <= ix < size()`.
    Returns:
      The possibly null attribute value at index `ix`; null if the attribute value is null.
    Throws:
      `NamingException` - If a naming exception was encountered while retrieving the value.

  - ### remove

    public Object remove(int ix)
    Description copied from interface: `Attribute`
    Removes an attribute value from the ordered list of attribute values. This method removes the value at the `ix` index of the list of attribute values. If the attribute values are unordered, this method removes the value that happens to be at that index. Values located at indices greater than `ix` are shifted up towards the front of the list (and their indices decremented by one).
    Specified by:
      `remove` in interface `Attribute`
    Parameters:
      `ix` - The index of the value to remove. `0 <= ix < size()`.
    Returns:
      The possibly null attribute value at index `ix` that was removed; null if the attribute value is null.

  - ### add

    public void add(int ix, Object attrVal)
    Description copied from interface: `Attribute`
    Adds an attribute value to the ordered list of attribute values. This method adds `attrVal` to the list of attribute values at index `ix`. Values located at indices at or greater than `ix` are shifted down towards the end of the list (and their indices incremented by one). If the attribute values are unordered and already have `attrVal`, `IllegalStateException` is thrown.
    Specified by:
      `add` in interface `Attribute`
    Parameters:
      `ix` - The index in the ordered list of attribute values to add the new value. `0 <= ix <= size()`.
      `attrVal` - The possibly null attribute value to add; if null, null is the value added.

  - ### set

    public Object set(int ix, Object attrVal)
    Description copied from interface: `Attribute`
    Sets an attribute value in the ordered list of attribute values. This method sets the value at the `ix` index of the list of attribute values to be `attrVal`. The old value is removed. If the attribute values are unordered, this method sets the value that happens to be at that index to `attrVal`, unless `attrVal` is already one of the values. In that case, `IllegalStateException` is thrown.
    Specified by:
      `set` in interface `Attribute`
    Parameters:
      `ix` - The index of the value in the ordered list of attribute values. `0 <= ix < size()`.
      `attrVal` - The possibly null attribute value to use. If null, 'null' replaces the old value.
    Returns:
      The possibly null attribute value at index ix that was replaced. Null if the attribute value was null.

  - ### getAttributeSyntaxDefinition

    public DirContext getAttributeSyntaxDefinition() throws NamingException
    Retrieves the syntax definition associated with this attribute.

    This method by default throws OperationNotSupportedException. A subclass should override this method if it supports schema.

    Specified by:
      `getAttributeSyntaxDefinition` in interface `Attribute`
    Returns:
      The attribute's syntax definition. Null if the implementation supports schemas but this particular attribute does not have any schema information.
    Throws:
      `OperationNotSupportedException` - If getting the schema is not supported.
      `NamingException` - If a naming exception occurs while getting the schema.

  - ### getAttributeDefinition

    public DirContext getAttributeDefinition() throws NamingException
    Retrieves this attribute's schema definition.

    This method by default throws OperationNotSupportedException. A subclass should override this method if it supports schema.

    Specified by:
      `getAttributeDefinition` in interface `Attribute`
    Returns:
      This attribute's schema definition. Null if the implementation supports schemas but this particular attribute does not have any schema information.
    Throws:
      `OperationNotSupportedException` - If getting the schema is not supported.
      `NamingException` - If a naming exception occurs while getting the schema.