Package io.vavr.collection

Class Tree.Empty<T>

  • Type Parameters:
    T - type of the tree's values
    All Implemented Interfaces:
    Foldable<T>, Traversable<T>, Iterable<T>, Value<T>, java.io.Serializable, java.lang.Iterable<T>
    Enclosing class:
    Tree<T>
    @Deprecated
public static final class Tree.Empty<T>
extends Tree<T>
implements java.io.Serializable
    Deprecated.
    will be removed from the public API
    The empty tree. Use Tree.empty() to create an instance.
    See Also:
    Serialized Form

    • Method Detail

      • instance

        public static <T> Tree.Empty<T> instance()
        Deprecated.

      • getChildren

        public List<Tree.Node<T>> getChildren()
        Deprecated.
        Description copied from class: Tree
        Returns the children of this tree.
        Specified by:
        getChildren in class Tree<T>
        Returns:
        the tree's children

      • getValue

        public T getValue()
        Deprecated.
        Description copied from class: Tree
        Gets the value of this tree.
        Specified by:
        getValue in class Tree<T>
        Returns:
        The value of this tree.

      • isEmpty

        public boolean isEmpty()
        Deprecated.
        Description copied from interface: Traversable
        Checks if this Traversable is empty.
        Specified by:
        isEmpty in interface Traversable<T>
        Specified by:
        isEmpty in interface Value<T>
        Returns:
        true, if this Traversable contains no elements, false otherwise.

      • length

        public int length()
        Deprecated.
        Description copied from interface: Traversable
        Computes the number of elements of this Traversable.

        Same as Traversable.size().

        Specified by:
        length in interface Traversable<T>
        Returns:
        the number of elements

      • isLeaf

        public boolean isLeaf()
        Deprecated.
        Description copied from class: Tree
        Checks if this Tree is a leaf. A tree is a leaf if it is a Node with no children. Because the empty tree is no Node, it is not a leaf by definition.
        Specified by:
        isLeaf in class Tree<T>
        Returns:
        true if this tree is a leaf, false otherwise.

      • equals

        public boolean equals​(java.lang.Object o)
        Deprecated.
        Description copied from interface: Traversable
        In Vavr there are four basic classes of collections:
        • Seq (sequential elements)
        • Set (distinct elements)
        • Map (indexed elements)
        • Multimap (indexed collections)
        Two collection instances of these classes are equal if and only if both collections
        • belong to the same basic collection class (Seq, Set, Map or Multimap)
        • contain the same elements
        • have the same element order, if the collections are of type Seq
        Two Map/Multimap elements, resp. entries, (key1, value1) and (key2, value2) are equal, if the keys are equal and the values are equal.

        Notes:

        • No collection instance equals null, e.g. Queue(1) not equals null.
        • Nulls are allowed and handled as expected, e.g. List(null, 1) equals Stream(null, 1) and HashMap((null, 1)) equals LinkedHashMap((null, 1)).
        • The element order is taken into account for Seq only. E.g. List(null, 1) not equals Stream(1, null) and HashMap((null, 1), ("a", null)) equals LinkedHashMap(("a", null), (null, 1)). The reason is, that we do not know which implementations we compare when having two instances of type Map, Multimap or Set (see Liskov Substitution Principle).
        • Other collection classes are equal if their types are equal and their elements are equal (in iteration order).
        • Iterator equality is defined to be object reference equality.
        Specified by:
        equals in interface Traversable<T>
        Specified by:
        equals in interface Value<T>
        Overrides:
        equals in class java.lang.Object
        Parameters:
        o - an object, may be null
        Returns:
        true, if this collection equals the given object according to the rules described above, false otherwise.

      • hashCode

        public int hashCode()
        Deprecated.
        Description copied from interface: Traversable
        Returns the hash code of this collection.
        We distinguish between two types of hashes, those for collections with predictable iteration order (like Seq) and those with arbitrary iteration order (like Set, Map and Multimap).
        In all cases the hash of an empty collection is defined to be 1.
        Collections with predictable iteration order are hashed as follows: 
        
 int hash = 1;
 for (T t : this) { hash = hash * 31 + Objects.hashCode(t); }
        Collections with arbitrary iteration order are hashed in a way such that the hash of a fixed number of elements is independent of their iteration order. 
        
 int hash = 1;
 for (T t : this) { hash += Objects.hashCode(t); }
        Please note that the particular hashing algorithms may change in a future version of Vavr.
        Generally, hash codes of collections aren't cached in Vavr (opposed to the size/length). Storing hash codes in order to reduce the time complexity would increase the memory footprint. Persistent collections are built upon tree structures, it allows us to implement efficient memory sharing. A drawback of tree structures is that they make it necessary to store collection attributes at each tree node (read: element).
        The computation of the hash code is linear in time, i.e. O(n). If the hash code of a collection is re-calculated often, e.g. when using a List as HashMap key, we might want to cache the hash code. This can be achieved by simply using a wrapper class, which is not included in Vavr but could be implemented like this: 
        public final class Hashed<K> {

     private final K key;
     private final Lazy<Integer> hashCode;

     public Hashed(K key) {
         this.key = key;
         this.hashCode = Lazy.of(() -> Objects.hashCode(key));
     }

     public K key() {
         return key;
     }

     &#64;Override
     public boolean equals(Object o) {
         if (o == key) {
             return true;
         } else if (key != null && o instanceof Hashed) {
             final Hashed that = (Hashed) o;
             return key.equals(that.key);
         } else {
             return false;
         }
     }

     &#64;Override
     public int hashCode() {
         return hashCode.get();
     }

     &#64;Override
     public String toString() {
         return "Hashed(" + (key == null ? "null" : key.toString()) + ")";
     }
 }
        Specified by:
        hashCode in interface Traversable<T>
        Specified by:
        hashCode in interface Value<T>
        Overrides:
        hashCode in class java.lang.Object
        Returns:
        The hash code of this collection

      • toString

        public java.lang.String toString()
        Deprecated.
        Description copied from interface: Value
        Clarifies that values have a proper toString() method implemented.

        See Object.toString().

        Specified by:
        toString in interface Value<T>
        Overrides:
        toString in class java.lang.Object
        Returns:
        A String representation of this object

      • toLispString

        public java.lang.String toLispString()
        Deprecated.
        Description copied from class: Tree
        Creates a Lisp-like representation of this Tree.
        Specified by:
        toLispString in class Tree<T>
        Returns:
        This Tree as Lisp-string, i.e. represented as list of lists.

      • draw

        public java.lang.String draw()
        Deprecated.
        Description copied from class: Tree
        Creates a neat 2-dimensional drawing of a tree. Unicode characters are used to draw node junctions.
        Specified by:
        draw in class Tree<T>
        Returns:
        A nice string representation of the tree.