Package it.unimi.dsi.fastutil.booleans

Class BooleanImmutableList

java.lang.Object
java.util.AbstractCollection<java.lang.Boolean>
it.unimi.dsi.fastutil.booleans.AbstractBooleanCollection
it.unimi.dsi.fastutil.booleans.AbstractBooleanList
it.unimi.dsi.fastutil.booleans.BooleanImmutableList
All Implemented Interfaces:
BooleanCollection, it.unimi.dsi.fastutil.booleans.BooleanIterable, BooleanList, BooleanStack, it.unimi.dsi.fastutil.Stack<java.lang.Boolean>, java.io.Serializable, java.lang.Cloneable, java.lang.Comparable<java.util.List<? extends java.lang.Boolean>>, java.lang.Iterable<java.lang.Boolean>, java.util.Collection<java.lang.Boolean>, java.util.List<java.lang.Boolean>, java.util.RandomAccess
public class BooleanImmutableList
extends AbstractBooleanList
implements BooleanList, java.util.RandomAccess, java.lang.Cloneable, java.io.Serializable
A type-specific array-based immutable list; provides some additional methods that use polymorphism to avoid (un)boxing.

Instances of this class are immutable and (contrarily to mutable array-based list implementations) the backing array is not exposed. Instances can be built using a variety of methods, but note that constructors using an array will not make a defensive copy.

This class implements the bulk method getElements() using high-performance system calls (e.g., System.arraycopy()) instead of expensive loops.

See Also:
Serialized Form

  • Constructor Details

    • BooleanImmutableList

      public BooleanImmutableList​(boolean[] a)
      Creates a new immutable list using a given array.

      Note that this constructor does not perform a defensive copy.

      Parameters:
      a - the array that will be used to back this immutable list.

    • BooleanImmutableList

      public BooleanImmutableList​(java.util.Collection<? extends java.lang.Boolean> c)
      Creates a new immutable list and fills it with a given collection.
      Parameters:
      c - a collection that will be used to fill the immutable list.

    • BooleanImmutableList

      public BooleanImmutableList​(BooleanCollection c)
      Creates a new immutable list and fills it with a given type-specific collection.
      Parameters:
      c - a type-specific collection that will be used to fill the immutable list.

    • BooleanImmutableList

      public BooleanImmutableList​(BooleanList l)
      Creates a new immutable list and fills it with a given type-specific list.
      Parameters:
      l - a type-specific list that will be used to fill the immutable list.

    • BooleanImmutableList

      public BooleanImmutableList​(boolean[] a, int offset, int length)
      Creates a new immutable list and fills it with the elements of a given array.
      Parameters:
      a - an array whose elements will be used to fill the immutable list.
      offset - the first element to use.
      length - the number of elements to use.

    • BooleanImmutableList

      public BooleanImmutableList​(it.unimi.dsi.fastutil.booleans.BooleanIterator i)
      Creates a new immutable list and fills it with the elements returned by a type-specific iterator..
      Parameters:
      i - a type-specific iterator whose returned elements will fill the immutable list.

  • Method Details

    • of

      public static BooleanImmutableList of()
      Returns an empty immutable list.
      Returns:
      an immutable list (possibly shared) that is empty.

    • of

      public static BooleanImmutableList of​(boolean... init)
      Creates an immutable list using a list of elements.

      Note that this method does not perform a defensive copy.

      Parameters:
      init - a list of elements that will be used to initialize the list.
      Returns:
      a new immutable list containing the given elements.

    • getBoolean

      public boolean getBoolean​(int index)
      Description copied from interface: BooleanList
      Returns the element at the specified position in this list.
      Specified by:
      getBoolean in interface BooleanList
      See Also:
      List.get(int)

    • indexOf

      public int indexOf​(boolean k)
      Description copied from interface: BooleanList
      Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
      Specified by:
      indexOf in interface BooleanList
      Overrides:
      indexOf in class AbstractBooleanList
      See Also:
      List.indexOf(Object)

    • lastIndexOf

      public int lastIndexOf​(boolean k)
      Description copied from interface: BooleanList
      Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
      Specified by:
      lastIndexOf in interface BooleanList
      Overrides:
      lastIndexOf in class AbstractBooleanList
      See Also:
      List.lastIndexOf(Object)

    • size

      public int size()
      Specified by:
      size in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      size in interface java.util.List<java.lang.Boolean>
      Specified by:
      size in class java.util.AbstractCollection<java.lang.Boolean>

    • isEmpty

      public boolean isEmpty()
      Specified by:
      isEmpty in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      isEmpty in interface java.util.List<java.lang.Boolean>
      Specified by:
      isEmpty in interface it.unimi.dsi.fastutil.Stack<java.lang.Boolean>
      Overrides:
      isEmpty in class java.util.AbstractCollection<java.lang.Boolean>

    • getElements

      public void getElements​(int from, boolean[] a, int offset, int length)
      Copies element of this type-specific list into the given array using optimized system calls.
      Specified by:
      getElements in interface BooleanList
      Overrides:
      getElements in class AbstractBooleanList
      Parameters:
      from - the start index (inclusive).
      a - the destination array.
      offset - the offset into the destination array where to store the first element copied.
      length - the number of elements to be copied.

    • forEach

      public void forEach​(BooleanConsumer action)
      Description copied from class: AbstractBooleanList
      Specified by:
      forEach in interface it.unimi.dsi.fastutil.booleans.BooleanIterable
      Overrides:
      forEach in class AbstractBooleanList

    • toBooleanArray

      public boolean[] toBooleanArray()
      Description copied from interface: BooleanCollection
      Returns a primitive type array containing the items of this collection.
      Specified by:
      toBooleanArray in interface BooleanCollection
      Overrides:
      toBooleanArray in class AbstractBooleanList
      Returns:
      a primitive type array containing the items of this collection.
      See Also:
      Collection.toArray()

    • toArray

      public boolean[] toArray​(boolean[] a)
      Description copied from interface: BooleanCollection
      Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.

      Note that, contrarily to Collection.toArray(Object[]), this methods just writes all elements of this collection: no special value will be added after the last one.

      Specified by:
      toArray in interface BooleanCollection
      Overrides:
      toArray in class AbstractBooleanList
      Parameters:
      a - if this array is big enough, it will be used to store this collection.
      Returns:
      a primitive type array containing the items of this collection.
      See Also:
      Collection.toArray(Object[])

    • listIterator

      public BooleanListIterator listIterator​(int index)
      Description copied from class: AbstractBooleanList
      Returns a type-specific list iterator on the list starting at a given index.
      Specified by:
      listIterator in interface BooleanList
      Specified by:
      listIterator in interface java.util.List<java.lang.Boolean>
      Overrides:
      listIterator in class AbstractBooleanList
      See Also:
      List.listIterator(int)

    • spliterator

      public BooleanSpliterator spliterator()
      Description copied from interface: BooleanList
      Returns a type-specific spliterator on the elements of this list.

      List spliterators must report at least Spliterator.SIZED and Spliterator.ORDERED.

      See List.spliterator() for more documentation on the requirements of the returned spliterator.

      Specified by:
      spliterator in interface BooleanCollection
      Specified by:
      spliterator in interface it.unimi.dsi.fastutil.booleans.BooleanIterable
      Specified by:
      spliterator in interface BooleanList
      Specified by:
      spliterator in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      spliterator in interface java.lang.Iterable<java.lang.Boolean>
      Specified by:
      spliterator in interface java.util.List<java.lang.Boolean>
      Returns:
      a type-specific spliterator on the elements of this collection.

    • subList

      public BooleanList subList​(int from, int to)
      Returns a type-specific view of the portion of this list from the index from, inclusive, to the index to, exclusive.
      Specified by:
      subList in interface BooleanList
      Specified by:
      subList in interface java.util.List<java.lang.Boolean>
      Overrides:
      subList in class AbstractBooleanList
      See Also:
      List.subList(int,int)
      API Notes:
      The returned list will be immutable, but is currently not declared to return an instance of ImmutableList due to complications of implementation details. This may change in a future version (in other words, do not consider the return type of this method to be stable if making a subclass of ImmutableList).

    • clone

      public BooleanImmutableList clone()

    • equals

      public boolean equals​(BooleanImmutableList l)
      Compares this type-specific immutable list to another one.
      Parameters:
      l - a type-specific immutable list.
      Returns:
      true if the argument contains the same elements of this type-specific immutable list.
      API Notes:
      This method exists only for sake of efficiency. The implementation inherited from the abstract implementation would already work.

    • equals

      public boolean equals​(java.lang.Object o)
      Specified by:
      equals in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      equals in interface java.util.List<java.lang.Boolean>
      Overrides:
      equals in class AbstractBooleanList

    • compareTo

      public int compareTo​(BooleanImmutableList l)
      Compares this immutable list to another immutable list.
      Parameters:
      l - an immutable list.
      Returns:
      a negative integer, zero, or a positive integer as this list is lexicographically less than, equal to, or greater than the argument.
      API Notes:
      This method exists only for sake of efficiency. The implementation inherited from the abstract implementation would already work.

    • compareTo

      public int compareTo​(java.util.List<? extends java.lang.Boolean> l)
      Description copied from class: AbstractBooleanList
      Compares this list to another object. If the argument is a List, this method performs a lexicographical comparison; otherwise, it throws a ClassCastException.
      Specified by:
      compareTo in interface java.lang.Comparable<java.util.List<? extends java.lang.Boolean>>
      Overrides:
      compareTo in class AbstractBooleanList
      Parameters:
      l - a list.
      Returns:
      if the argument is a List, a negative integer, zero, or a positive integer as this list is lexicographically less than, equal to, or greater than the argument.

    • add

      @Deprecated public final void add​(int index, boolean k)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Inserts the specified element at the specified position in this list (optional operation).
      Specified by:
      add in interface BooleanList
      Overrides:
      add in class AbstractBooleanList
      See Also:
      List.add(int,Object)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • add

      @Deprecated public final boolean add​(boolean k)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Ensures that this collection contains the specified element (optional operation).
      Specified by:
      add in interface BooleanCollection
      Specified by:
      add in interface BooleanList
      Overrides:
      add in class AbstractBooleanList
      See Also:
      Collection.add(Object)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • addAll

      @Deprecated public final boolean addAll​(java.util.Collection<? extends java.lang.Boolean> c)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Specified by:
      addAll in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      addAll in interface java.util.List<java.lang.Boolean>
      Overrides:
      addAll in class AbstractBooleanList
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • addAll

      @Deprecated public final boolean addAll​(int index, java.util.Collection<? extends java.lang.Boolean> c)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Adds all of the elements in the specified collection to this list (optional operation).
      Specified by:
      addAll in interface java.util.List<java.lang.Boolean>
      Overrides:
      addAll in class AbstractBooleanList
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • removeBoolean

      @Deprecated public final boolean removeBoolean​(int index)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Removes the element at the specified position in this list (optional operation).
      Specified by:
      removeBoolean in interface BooleanList
      Overrides:
      removeBoolean in class AbstractBooleanList
      See Also:
      List.remove(int)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • rem

      @Deprecated public final boolean rem​(boolean k)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Removes a single instance of the specified element from this collection, if it is present (optional operation).
      Specified by:
      rem in interface BooleanCollection
      Overrides:
      rem in class AbstractBooleanList
      See Also:
      List.remove(Object)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • removeAll

      @Deprecated public final boolean removeAll​(java.util.Collection<?> c)
      Deprecated.
      Description copied from class: AbstractBooleanCollection
      Specified by:
      removeAll in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      removeAll in interface java.util.List<java.lang.Boolean>
      Overrides:
      removeAll in class AbstractBooleanCollection
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • retainAll

      @Deprecated public final boolean retainAll​(java.util.Collection<?> c)
      Deprecated.
      Description copied from class: AbstractBooleanCollection
      Specified by:
      retainAll in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      retainAll in interface java.util.List<java.lang.Boolean>
      Overrides:
      retainAll in class AbstractBooleanCollection
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • removeIf

      @Deprecated public final boolean removeIf​(java.util.function.Predicate<? super java.lang.Boolean> c)
      Deprecated.
      Description copied from interface: BooleanCollection
      Specified by:
      removeIf in interface BooleanCollection
      Specified by:
      removeIf in interface java.util.Collection<java.lang.Boolean>
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • removeIf

      @Deprecated public final boolean removeIf​(BooleanPredicate c)
      Deprecated.
      Description copied from interface: BooleanCollection
      Remove from this collection all elements which satisfy the given predicate.
      Specified by:
      removeIf in interface BooleanCollection
      Parameters:
      c - a predicate which returns true for elements to be removed.
      Returns:
      true if any elements were removed.
      See Also:
      Collection.removeIf(java.util.function.Predicate)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • replaceAll

      @Deprecated public final void replaceAll​(java.util.function.UnaryOperator<java.lang.Boolean> operator)
      Deprecated.
      Description copied from interface: BooleanList
      Specified by:
      replaceAll in interface BooleanList
      Specified by:
      replaceAll in interface java.util.List<java.lang.Boolean>
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • add

      @Deprecated public final void add​(int index, java.lang.Boolean k)
      Deprecated.
      Description copied from interface: BooleanList
      Specified by:
      add in interface BooleanList
      Specified by:
      add in interface java.util.List<java.lang.Boolean>
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • add

      @Deprecated public final boolean add​(java.lang.Boolean k)
      Deprecated.
      Description copied from class: AbstractBooleanCollection
      Specified by:
      add in interface BooleanCollection
      Specified by:
      add in interface BooleanList
      Specified by:
      add in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      add in interface java.util.List<java.lang.Boolean>
      Overrides:
      add in class AbstractBooleanCollection
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • remove

      @Deprecated public final java.lang.Boolean remove​(int index)
      Deprecated.
      Description copied from interface: BooleanList
      Specified by:
      remove in interface BooleanList
      Specified by:
      remove in interface java.util.List<java.lang.Boolean>
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • remove

      @Deprecated public final boolean remove​(java.lang.Object k)
      Deprecated.
      Description copied from class: AbstractBooleanCollection
      Specified by:
      remove in interface BooleanCollection
      Specified by:
      remove in interface BooleanList
      Specified by:
      remove in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      remove in interface java.util.List<java.lang.Boolean>
      Overrides:
      remove in class AbstractBooleanCollection
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • set

      @Deprecated public final java.lang.Boolean set​(int index, java.lang.Boolean k)
      Deprecated.
      Description copied from interface: BooleanList
      Specified by:
      set in interface BooleanList
      Specified by:
      set in interface java.util.List<java.lang.Boolean>
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • addAll

      @Deprecated public final boolean addAll​(BooleanCollection c)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Adds all elements of the given type-specific collection to this collection.
      Specified by:
      addAll in interface BooleanCollection
      Overrides:
      addAll in class AbstractBooleanList
      Parameters:
      c - a type-specific collection.
      Returns:
      true if this collection changed as a result of the call.
      See Also:
      Collection.addAll(Collection)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • addAll

      @Deprecated public final boolean addAll​(BooleanList c)
      Deprecated.
      Description copied from interface: BooleanList
      Appends all of the elements in the specified type-specific list to the end of this type-specific list (optional operation).
      Specified by:
      addAll in interface BooleanList
      See Also:
      List.addAll(Collection)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • addAll

      @Deprecated public final boolean addAll​(int index, BooleanCollection c)
      Deprecated.
      Description copied from interface: BooleanList
      Inserts all of the elements in the specified type-specific collection into this type-specific list at the specified position (optional operation).
      Specified by:
      addAll in interface BooleanList
      Overrides:
      addAll in class AbstractBooleanList
      See Also:
      List.addAll(int,java.util.Collection)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • addAll

      @Deprecated public final boolean addAll​(int index, BooleanList c)
      Deprecated.
      Description copied from interface: BooleanList
      Inserts all of the elements in the specified type-specific list into this type-specific list at the specified position (optional operation).
      Specified by:
      addAll in interface BooleanList
      See Also:
      List.addAll(int,Collection)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • removeAll

      @Deprecated public final boolean removeAll​(BooleanCollection c)
      Deprecated.
      Description copied from interface: BooleanCollection
      Remove from this collection all elements in the given type-specific collection.
      Specified by:
      removeAll in interface BooleanCollection
      Overrides:
      removeAll in class AbstractBooleanCollection
      Parameters:
      c - a type-specific collection.
      Returns:
      true if this collection changed as a result of the call.
      See Also:
      Collection.removeAll(Collection)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • retainAll

      @Deprecated public final boolean retainAll​(BooleanCollection c)
      Deprecated.
      Description copied from interface: BooleanCollection
      Retains in this collection only elements from the given type-specific collection.
      Specified by:
      retainAll in interface BooleanCollection
      Overrides:
      retainAll in class AbstractBooleanCollection
      Parameters:
      c - a type-specific collection.
      Returns:
      true if this collection changed as a result of the call.
      See Also:
      Collection.retainAll(Collection)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • set

      @Deprecated public final boolean set​(int index, boolean k)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Replaces the element at the specified position in this list with the specified element (optional operation).
      Specified by:
      set in interface BooleanList
      Overrides:
      set in class AbstractBooleanList
      See Also:
      List.set(int,Object)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • clear

      @Deprecated public final void clear()
      Deprecated.
      Description copied from class: AbstractBooleanList
      Specified by:
      clear in interface java.util.Collection<java.lang.Boolean>
      Specified by:
      clear in interface java.util.List<java.lang.Boolean>
      Overrides:
      clear in class AbstractBooleanList
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • size

      @Deprecated public final void size​(int size)
      Deprecated.
      Description copied from interface: BooleanList
      Sets the size of this list.

      If the specified size is smaller than the current size, the last elements are discarded. Otherwise, they are filled with 0/null/false.

      Specified by:
      size in interface BooleanList
      Overrides:
      size in class AbstractBooleanList
      Parameters:
      size - the new size.
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • removeElements

      @Deprecated public final void removeElements​(int from, int to)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Removes (hopefully quickly) elements of this type-specific list.

      This is a trivial iterator-based based implementation. It is expected that implementations will override this method with a more optimized version.

      Specified by:
      removeElements in interface BooleanList
      Overrides:
      removeElements in class AbstractBooleanList
      Parameters:
      from - the start index (inclusive).
      to - the end index (exclusive).
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • addElements

      @Deprecated public final void addElements​(int index, boolean[] a, int offset, int length)
      Deprecated.
      Description copied from class: AbstractBooleanList
      Add (hopefully quickly) elements to this type-specific list.

      This is a trivial iterator-based implementation. It is expected that implementations will override this method with a more optimized version.

      Specified by:
      addElements in interface BooleanList
      Overrides:
      addElements in class AbstractBooleanList
      Parameters:
      index - the index at which to add elements.
      a - the array containing the elements.
      offset - the offset of the first element to add.
      length - the number of elements to add.
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • setElements

      @Deprecated public final void setElements​(int index, boolean[] a, int offset, int length)
      Deprecated.
      Description copied from interface: BooleanList
      Set (hopefully quickly) elements to match the array given. Sets each in this list to the corresponding elements in the array, as if by 
      
 ListIterator iter = listIterator(index);
 int i = 0;
 while (i < length) {
   iter.next();
   iter.set(a[offset + i++]);
 }
      However, the exact implementation may be more efficient, taking into account whether random access is faster or not, or at the discretion of subclasses, abuse internals.
      Specified by:
      setElements in interface BooleanList
      Overrides:
      setElements in class AbstractBooleanList
      Parameters:
      index - the index at which to start setting elements.
      a - the array containing the elements
      offset - the offset of the first element to add.
      length - the number of elements to add.
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • sort

      @Deprecated public final void sort​(BooleanComparator comp)
      Deprecated.
      Description copied from interface: BooleanList
      Sort a list using a type-specific comparator.

      Pass null to sort using natural ordering.

      Specified by:
      sort in interface BooleanList
      See Also:
      List.sort(java.util.Comparator)
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • unstableSort

      @Deprecated public final void unstableSort​(BooleanComparator comp)
      Deprecated.
      Description copied from interface: BooleanList
      Sorts this list using a sort not assured to be stable.

      Pass null to sort using natural ordering.

      This differs from List.sort(java.util.Comparator) in that the results are not assured to be stable, but may be a bit faster.

      Unless a subclass specifies otherwise, the results of the method if the list is concurrently modified during the sort are unspecified.

      Specified by:
      unstableSort in interface BooleanList
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • sort

      @Deprecated public final void sort​(java.util.Comparator<? super java.lang.Boolean> comparator)
      Deprecated.
      Description copied from interface: BooleanList
      Specified by:
      sort in interface BooleanList
      Specified by:
      sort in interface java.util.List<java.lang.Boolean>
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.

    • unstableSort

      @Deprecated public final void unstableSort​(java.util.Comparator<? super java.lang.Boolean> comparator)
      Deprecated.
      Description copied from interface: BooleanList
      Sorts this list using a sort not assured to be stable.
      Specified by:
      unstableSort in interface BooleanList
      Implementation Specification:
      Always throws UnsupportedOperationException as this is an immutable type.