Package org.docx4j.com.google.common.collect

Class ImmutableCollection<E>

java.lang.Object

java.util.AbstractCollection<E>

org.docx4j.com.google.common.collect.ImmutableCollection<E>

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable<E>, java.util.Collection<E>

Direct Known Subclasses:

ImmutableSet

@GwtCompatible(emulated=true)
public abstract class ImmutableCollection<E>
extends java.util.AbstractCollection<E>
implements java.io.Serializable

A Collection whose contents will never change, and which offers a few additional guarantees detailed below.

Warning: avoid direct usage of ImmutableCollection as a type (just as with Collection itself). Prefer subtypes such as ImmutableSet or ImmutableList, which have well-defined Object.equals(java.lang.Object) semantics, thus avoiding a common source of bugs and confusion.

About all Immutable- collections

The remainder of this documentation applies to every public Immutable- type in this package, whether it is a subtype of ImmutableCollection or not.

Guarantees

Each makes the following guarantees:

• Shallow immutability. Elements can never be added, removed or replaced in this collection. This is a stronger guarantee than that of Collections.unmodifiableCollection(java.util.Collection<? extends T>), whose contents change whenever the wrapped collection is modified.
• Null-hostility. This collection will never contain a null element.
• Deterministic iteration. The iteration order is always well-defined, depending on how the collection was created. Typically this is insertion order unless an explicit ordering is otherwise specified (e.g. ImmutableSortedSet#naturalOrder). See the appropriate factory method for details. View collections such as ImmutableMultiset#elementSet iterate in the same order as the parent, except as noted.
• Thread safety. It is safe to access this collection concurrently from multiple threads.
• Integrity. This type cannot be subclassed outside this package (which would allow these guarantees to be violated).

"Interfaces", not implementations

These are classes instead of interfaces to prevent external subtyping, but should be thought of as interfaces in every important sense. Each public class such as ImmutableSet is a type offering meaningful behavioral guarantees. This is substantially different from the case of (say) HashSet, which is an implementation, with semantics that were largely defined by its supertype.

For field types and method return types, you should generally use the immutable type (such as ImmutableList) instead of the general collection interface type (such as List). This communicates to your callers all of the semantic guarantees listed above, which is almost always very useful information.

On the other hand, a parameter type of ImmutableList is generally a nuisance to callers. Instead, accept Iterable and have your method or constructor body pass it to the appropriate copyOf method itself.

Expressing the immutability guarantee directly in the type that user code references is a powerful advantage. Although Java offers certain immutable collection factory methods, such as Collections.singleton(Object) and Set.of, we recommend using these classes instead for this reason (as well as for consistency).

Creation

Except for logically "abstract" types like ImmutableCollection itself, each Immutable type provides the static operations you need to obtain instances of that type. These usually include:

• Static methods named of, accepting an explicit list of elements or entries.
• Static methods named copyOf (or copyOfSorted), accepting an existing collection whose contents should be copied.
• A static nested Builder class which can be used to populate a new immutable instance.

Warnings

• Warning: as with any collection, it is almost always a bad idea to modify an element (in a way that affects its Object.equals(java.lang.Object) behavior) while it is contained in a collection. Undefined behavior and bugs will result. It's generally best to avoid using mutable objects as elements at all, as many users may expect your "immutable" object to be deeply immutable.

Performance notes

• Implementations can be generally assumed to prioritize memory efficiency, then speed of access, and lastly speed of creation.
• The copyOf methods will sometimes recognize that the actual copy operation is unnecessary; for example, copyOf(copyOf(anArrayList)) should copy the data only once. This reduces the expense of habitually making defensive copies at API boundaries. However, the precise conditions for skipping the copy operation are undefined.
• Warning: a view collection such as Map.keySet() or ImmutableList#subList may retain a reference to the entire data set, preventing it from being garbage collected. If some of the data is no longer reachable through other means, this constitutes a memory leak. Pass the view collection to the appropriate copyOf method to obtain a correctly-sized copy.
• The performance of using the associated Builder class can be assumed to be no worse, and possibly better, than creating a mutable collection and copying it.
• Implementations generally do not cache hash codes. If your element or key type has a slow hashCode implementation, it should cache it itself.

Example usage

 class Foo {
   private static final ImmutableSet<String> RESERVED_CODES =
       ImmutableSet.of("AZ", "CQ", "ZX");

   private final ImmutableSet<String> codes;

   public Foo(Iterable<String> codes) {
     this.codes = ImmutableSet.copyOf(codes);
     checkArgument(Collections.disjoint(this.codes, RESERVED_CODES));
   }
 }
 

See also

See the Guava User Guide article on immutable collections.

Since:

2.0

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ImmutableCollection.Builder<E>	Abstract base class for builders of ImmutableCollection types.

Method Summary

Modifier and Type	Method	Description
boolean	add(E e)	Deprecated. Unsupported operation.
boolean	addAll(java.util.Collection<? extends E> newElements)	Deprecated. Unsupported operation.
void	clear()	Deprecated. Unsupported operation.
abstract boolean	contains(@Nullable java.lang.Object object)
abstract UnmodifiableIterator<E>	iterator()	Returns an unmodifiable iterator across the elements in this collection.
boolean	remove(java.lang.Object object)	Deprecated. Unsupported operation.
boolean	removeAll(java.util.Collection<?> oldElements)	Deprecated. Unsupported operation.
boolean	removeIf(java.util.function.Predicate<? super E> filter)	Deprecated. Unsupported operation.
boolean	retainAll(java.util.Collection<?> elementsToKeep)	Deprecated. Unsupported operation.
java.util.Spliterator<E>	spliterator()
java.lang.Object[]	toArray()
<T> T[]	toArray(T[] other)

Methods inherited from class java.util.AbstractCollection

containsAll, isEmpty, size, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

equals, hashCode, parallelStream, stream, toArray

Methods inherited from interface java.lang.Iterable

forEach

Method Details

iterator

public abstract UnmodifiableIterator<E> iterator()

Returns an unmodifiable iterator across the elements in this collection.

Specified by:

iterator in interface java.util.Collection<E>

Specified by:

iterator in interface java.lang.Iterable<E>

Specified by:

iterator in class java.util.AbstractCollection<E>

spliterator

public java.util.Spliterator<E> spliterator()

Specified by:

spliterator in interface java.util.Collection<E>

Specified by:

spliterator in interface java.lang.Iterable<E>

toArray

public final java.lang.Object[] toArray()

Specified by:

toArray in interface java.util.Collection<E>

Overrides:

toArray in class java.util.AbstractCollection<E>

toArray

@CanIgnoreReturnValue public final <T> T[] toArray(T[] other)

Specified by:

toArray in interface java.util.Collection<E>

Overrides:

toArray in class java.util.AbstractCollection<E>

contains

public abstract boolean contains(@Nullable java.lang.Object object)

Specified by:

contains in interface java.util.Collection<E>

Overrides:

contains in class java.util.AbstractCollection<E>

add

@CanIgnoreReturnValue @Deprecated public final boolean add(E e)

Deprecated.

Unsupported operation.

Guaranteed to throw an exception and leave the collection unmodified.

Specified by:

add in interface java.util.Collection<E>

Overrides:

add in class java.util.AbstractCollection<E>

Throws:

java.lang.UnsupportedOperationException - always

remove

@CanIgnoreReturnValue @Deprecated public final boolean remove(java.lang.Object object)

Deprecated.

Unsupported operation.

Guaranteed to throw an exception and leave the collection unmodified.

Specified by:

remove in interface java.util.Collection<E>

Overrides:

remove in class java.util.AbstractCollection<E>

Throws:

java.lang.UnsupportedOperationException - always

addAll

@CanIgnoreReturnValue @Deprecated public final boolean addAll(java.util.Collection<? extends E> newElements)

Deprecated.

Unsupported operation.

Guaranteed to throw an exception and leave the collection unmodified.

Specified by:

addAll in interface java.util.Collection<E>

Overrides:

addAll in class java.util.AbstractCollection<E>

Throws:

java.lang.UnsupportedOperationException - always

removeAll

@CanIgnoreReturnValue @Deprecated public final boolean removeAll(java.util.Collection<?> oldElements)

Deprecated.

Unsupported operation.

Guaranteed to throw an exception and leave the collection unmodified.

Specified by:

removeAll in interface java.util.Collection<E>

Overrides:

removeAll in class java.util.AbstractCollection<E>

Throws:

java.lang.UnsupportedOperationException - always

removeIf

@CanIgnoreReturnValue @Deprecated public final boolean removeIf(java.util.function.Predicate<? super E> filter)

Deprecated.

Unsupported operation.

Guaranteed to throw an exception and leave the collection unmodified.

Specified by:

removeIf in interface java.util.Collection<E>

Throws:

java.lang.UnsupportedOperationException - always

retainAll

@Deprecated public final boolean retainAll(java.util.Collection<?> elementsToKeep)

Deprecated.

Unsupported operation.

Guaranteed to throw an exception and leave the collection unmodified.

Specified by:

retainAll in interface java.util.Collection<E>

Overrides:

retainAll in class java.util.AbstractCollection<E>

Throws:

java.lang.UnsupportedOperationException - always

clear

@Deprecated public final void clear()

Deprecated.

Unsupported operation.

Guaranteed to throw an exception and leave the collection unmodified.

Specified by:

clear in interface java.util.Collection<E>

Overrides:

clear in class java.util.AbstractCollection<E>

Throws:

java.lang.UnsupportedOperationException - always