Initializer
SingletonMap(Key->Item entry)
Attributes
entrySource Codeshared Key->Item entry
hashSource Codeshared actual Integer hash

The hash value of the value, which allows the value to be an element of a hash-based set or key of a hash-based map. Implementations must respect the constraint that:

  • if x==y then x.hash==y.hash.

Therefore, a class which refines equals must also refine hash.

Because the Integer type is platform-dependent a compiler for a given platform is permitted to further manipulate the calculated hash for an object, and the resulting hash may differ between platforms.

Refines Map.hash ultimately refines Object.hash
Inherited Attributes
Attributes inherited from: Object
Attributes inherited from: Collection<Element>
Attributes inherited from: Correspondence<Key,Item>
Attributes inherited from: Iterable<Element,Absent>
Attributes inherited from: Map<Key,Item>
Methods
cloneSource Codeshared actual SingletonMap<Key,Item> clone()

A shallow copy of this collection, that is, a collection with identical elements which does not change if this collection changes. If this collection is immutable, it is acceptable to return a reference to this collection. If this collection is mutable, a newly instantiated collection must be returned.

Refines Map.clone ultimately refines Collection.clone
containsSource Codeshared actual Boolean contains(Object entry)

Returns true if the given value belongs to this Category, that is, if it is an element of this Category, or false otherwise.

For most Categorys the following relationship is satisfied by every pair of elements x and y:

  • if x==y, then x in category == y in category

However, it is possible to form a useful Category consistent with some other equivalence relation, for example ===. Therefore implementations of contains() which do not satisfy this relationship are tolerated.

Refines Map.contains ultimately refines Category.contains
definesSource Codeshared actual Boolean defines(Object key)

Determines if there is a value defined for the given key.

Refines Map.defines ultimately refines Correspondence.defines
eachSource Codeshared actual void each(void step(Key->Item element))

Call the given function (step) for each element of this stream, passing the elements in the order they occur in this stream.

For example:

words.each((word) {
    print(word.lowercased);
    print(word.uppercased);
});

Has the same effect as the following for loop:

for (word in words) {
    print(word.lowercased);
    print(word.uppercased);
}

For certain streams this method is highly efficient, surpassing the performance of for loops on the JVM. Thus, each() is sometimes preferred in highly performance-critical low-level code.

equalsSource Codeshared actual Boolean equals(Object that)

Determine if two values are equal. Implementations should respect the constraints that:

  • if x===y then x==y (reflexivity),
  • if x==y then y==x (symmetry),
  • if x==y and y==z then x==z (transitivity).

Furthermore it is recommended that implementations ensure that if x==y then x and y have the same concrete class.

A class which explicitly refines equals() is said to support value equality, and the equality operator == is considered much more meaningful for such classes than for a class which simply inherits the default implementation of identity equality from Identifiable.

Refines Map.equals ultimately refines Object.equals
getSource Codeshared actual Item? get(Object key)

Returns the value defined for the given key, or null if there is no value defined for the given key.

Refines Map.get ultimately refines Correspondence.get
iteratorSource Codeshared actual Iterator<Key->Item> iterator()

An iterator for the elements belonging to this stream.

Inherited Methods
Methods inherited from: Object
Methods inherited from: Category<Element>
Methods inherited from: Collection<Element>
Methods inherited from: Correspondence<Key,Item>
Methods inherited from: Iterable<Element,Absent>
Methods inherited from: Map<Key,Item>