org.apache.commons.collections4.collection

## Class PredicatedCollection<E>

- java.lang.Object
- - org.apache.commons.collections4.collection.AbstractCollectionDecorator<E>
  - - org.apache.commons.collections4.collection.PredicatedCollection<E>

- Type Parameters:
    `E` - the type of the elements in the collection
  All Implemented Interfaces:
    Serializable, Iterable<E>, Collection<E>
  Direct Known Subclasses:
    PredicatedBag, PredicatedList, PredicatedQueue, PredicatedSet

      public class PredicatedCollection<E>
      extends AbstractCollectionDecorator<E>

  Decorates another `Collection` to validate that additions match a specified predicate.

  This collection exists to provide validation for the decorated collection. It is normally created to decorate an empty collection. If an object cannot be added to the collection, an IllegalArgumentException is thrown.

  One usage would be to ensure that no null entries are added to the collection.

      Collection coll = PredicatedCollection.decorate(new ArrayList(), NotNullPredicate.INSTANCE);

  This class is Serializable from Commons Collections 3.1.

  Since:
    3.0
  Version:
    $Id: PredicatedCollection.java 1479401 2013-05-05 21:51:47Z tn $
  See Also:
    Serialized Form

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected Predicate<? super E>` | `predicate` The predicate to use

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `PredicatedCollection(Collection<E> coll, Predicate<? super E> predicate)` Constructor that wraps (not copies).

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `add(E object)` Override to validate the object being added to ensure it matches the predicate.
    `boolean` | `addAll(Collection<? extends E> coll)` Override to validate the objects being added to ensure they match the predicate.
    `static <T> PredicatedCollection<T>` | `predicatedCollection(Collection<T> coll, Predicate<? super T> predicate)` Factory method to create a predicated (validating) collection.
    `protected void` | `validate(E object)` Validates the object being added to ensure it matches the predicate.

    - ### Methods inherited from class org.apache.commons.collections4.collection.AbstractCollectionDecorator

      `clear, contains, containsAll, decorated, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, setCollection, size, toArray, toArray, toString`

    - ### Methods inherited from class java.lang.Object

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

- - ### Field Detail

    - #### predicate

          protected final Predicate<? super E> predicate

      The predicate to use

  - ### Constructor Detail

    - #### PredicatedCollection

          protected PredicatedCollection(Collection<E> coll,
                              Predicate<? super E> predicate)

      Constructor that wraps (not copies).

      If there are any elements already in the collection being decorated, they are validated.

      Parameters:
        `coll` - the collection to decorate, must not be null
        `predicate` - the predicate to use for validation, must not be null
      Throws:
        `IllegalArgumentException` - if collection or predicate is null
        `IllegalArgumentException` - if the collection contains invalid elements

  - ### Method Detail

    - #### predicatedCollection

          public static <T> PredicatedCollection<T> predicatedCollection(Collection<T> coll,
                                                         Predicate<? super T> predicate)

      Factory method to create a predicated (validating) collection.

      If there are any elements already in the collection being decorated, they are validated.

      Type Parameters:
        `T` - the type of the elements in the collection
      Parameters:
        `coll` - the collection to decorate, must not be null
        `predicate` - the predicate to use for validation, must not be null
      Returns:
        a new predicated collection
      Throws:
        `IllegalArgumentException` - if collection or predicate is null
        `IllegalArgumentException` - if the collection contains invalid elements
      Since:
        4.0

    - #### validate

          protected void validate(E object)

      Validates the object being added to ensure it matches the predicate.

      The predicate itself should not throw an exception, but return false to indicate that the object cannot be added.

      Parameters:
        `object` - the object being added
      Throws:
        `IllegalArgumentException` - if the add is invalid

    - #### add

          public boolean add(E object)

      Override to validate the object being added to ensure it matches the predicate.
      Specified by:
        `add` in interface `Collection<E>`
      Overrides:
        `add` in class `AbstractCollectionDecorator<E>`
      Parameters:
        `object` - the object being added
      Returns:
        the result of adding to the underlying collection
      Throws:
        `IllegalArgumentException` - if the add is invalid

    - #### addAll

          public boolean addAll(Collection<? extends E> coll)

      Override to validate the objects being added to ensure they match the predicate. If any one fails, no update is made to the underlying collection.
      Specified by:
        `addAll` in interface `Collection<E>`
      Overrides:
        `addAll` in class `AbstractCollectionDecorator<E>`
      Parameters:
        `coll` - the collection being added
      Returns:
        the result of adding to the underlying collection
      Throws:
        `IllegalArgumentException` - if the add is invalid

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