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  /*
   * Copyright (C) 2007 The Guava Authors
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 package com.google.common.collect;
 
 
 
 import  javax.annotation.Nullable;

A collection which forwards all its method calls to another collection. Subclasses should override one or more methods to modify the behavior of the backing collection as desired per the decorator pattern.

Warning: The methods of ForwardingCollection forward indiscriminately to the methods of the delegate. For example, overriding add alone will not change the behavior of addAll, which can lead to unexpected behavior. In this case, you should override addAll as well, either providing your own implementation, or delegating to the provided standardAddAll method.

The standard methods are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe.

Author(s):
Kevin Bourrillion
Louis Wasserman
Since:
2.0 (imported from Google Collections Library)
 
 public abstract class ForwardingCollection<E> extends ForwardingObject
     implements Collection<E> {
   // TODO(user): identify places where thread safety is actually lost
 
  
Constructor for use by subclasses.
 
   protected ForwardingCollection() {}
 
   @Override protected abstract Collection<E> delegate();
 
   @Override
   public Iterator<E> iterator() {
     return delegate().iterator();
   }
 
   @Override
   public int size() {
     return delegate().size();
   }
 
   @Override
   public boolean removeAll(Collection<?> collection) {
     return delegate().removeAll(collection);
   }
 
   @Override
   public boolean isEmpty() {
     return delegate().isEmpty();
   }
 
   @Override
   public boolean contains(Object object) {
     return delegate().contains(object);
   }
 
   @Override
   public boolean add(E element) {
     return delegate().add(element);
   }
 
   @Override
   public boolean remove(Object object) {
     return delegate().remove(object);
   }
 
   @Override
   public boolean containsAll(Collection<?> collection) {
     return delegate().containsAll(collection);
   }
 
   @Override
   public boolean addAll(Collection<? extends E> collection) {
     return delegate().addAll(collection);
  }
  public boolean retainAll(Collection<?> collection) {
    return delegate().retainAll(collection);
  }
  public void clear() {
    delegate().clear();
  }
  public Object[] toArray() {
    return delegate().toArray();
  }
  public <T> T[] toArray(T[] array) {
    return delegate().toArray(array);
  }

  
A sensible definition of contains in terms of iterator. If you override iterator, you may wish to override contains to forward to this implementation.

Since:
7.0
  protected boolean standardContains(@Nullable Object object) {
    return Iterators.contains(iterator(), object);
  }

  
A sensible definition of containsAll in terms of contains . If you override contains, you may wish to override containsAll to forward to this implementation.

Since:
7.0
  protected boolean standardContainsAll(Collection<?> collection) {
    return Collections2.containsAllImpl(thiscollection);
  }

  
A sensible definition of addAll in terms of add. If you override add, you may wish to override addAll to forward to this implementation.

Since:
7.0
  protected boolean standardAddAll(Collection<? extends E> collection) {
    return Iterators.addAll(thiscollection.iterator());
  }

  
A sensible definition of remove in terms of iterator, using the iterator's remove method. If you override iterator, you may wish to override remove to forward to this implementation.

Since:
7.0
  protected boolean standardRemove(@Nullable Object object) {
    Iterator<E> iterator = iterator();
    while (iterator.hasNext()) {
      if (Objects.equal(iterator.next(), object)) {
        iterator.remove();
        return true;
      }
    }
    return false;
  }

  
A sensible definition of removeAll in terms of iterator, using the iterator's remove method. If you override iterator, you may wish to override removeAll to forward to this implementation.

Since:
7.0
  protected boolean standardRemoveAll(Collection<?> collection) {
    return Iterators.removeAll(iterator(), collection);
  }

  
A sensible definition of retainAll in terms of iterator, using the iterator's remove method. If you override iterator, you may wish to override retainAll to forward to this implementation.

Since:
7.0
  protected boolean standardRetainAll(Collection<?> collection) {
    return Iterators.retainAll(iterator(), collection);
  }

  
A sensible definition of clear in terms of iterator, using the iterator's remove method. If you override iterator, you may wish to override clear to forward to this implementation.

Since:
7.0
  protected void standardClear() {
    Iterators.clear(iterator());
  }

  
A sensible definition of isEmpty as !iterator().hasNext. If you override isEmpty, you may wish to override isEmpty to forward to this implementation. Alternately, it may be more efficient to implement isEmpty as size() == 0.

Since:
7.0
  protected boolean standardIsEmpty() {
    return !iterator().hasNext();
  }

  
A sensible definition of toString in terms of iterator. If you override iterator, you may wish to override toString to forward to this implementation.

Since:
7.0
  protected String standardToString() {
    return Collections2.toStringImpl(this);
  }

  
A sensible definition of toArray() in terms of toArray(Object[]). If you override toArray(Object[]), you may wish to override toArray to forward to this implementation.

Since:
7.0
  protected Object[] standardToArray() {
    Object[] newArray = new Object[size()];
    return toArray(newArray);
  }

  
A sensible definition of toArray(Object[]) in terms of size and iterator. If you override either of these methods, you may wish to override toArray to forward to this implementation.

Since:
7.0
  protected <T> T[] standardToArray(T[] array) {
    return ObjectArrays.toArrayImpl(thisarray);
  }
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