Continued developing of optional class

Author: alemazzo

stream/optional.py

@@ -1,25 +1,125 @@
 class Optional:
 
+    '''
+    A container object which may or may not contain a non-null value. If a value is present, isPresent() returns true. If no value is present, the object is considered empty and isPresent() returns false.
+
+    Additional methods that depend on the presence or absence of a contained value are provided, such as orElse() (returns a default value if no value is present) and ifPresent() (performs an action if a value is present). 
+    '''
+
+    '''
+    STATIC METHODS
+    '''
+
+    @staticmethod
+    def empty():
+        '''
+        Returns an empty Optional instance. No value is present for this Optional.
+
+        :return: an empty Optional
+        '''
+        return Optional(None)
+
     @staticmethod
     def of(elem):
+        '''
+        Returns an Optional describing the given non-null value.
+
+        :param T elem: the value to describe, which must be non-null
+        :return: an Optional with the value present
+        :raise: Exception if the value is null
+        '''
         if elem is None:
             raise Exception("Optional Empty")
         return Optional(elem)
 
     @staticmethod
     def ofNullable(elem):
+        '''
+        Returns an Optional describing the given value, if non-null, otherwise returns an empty Optional.
+
+        :param T elem: the possibly-null value to describe
+        :return: an Optional with a present value if the specified value is non-null, otherwise an empty Optional
+        '''
         return Optional(elem)
 
+    '''
+    NON STATIC METHODS
+    '''
+
     def __init__(self, elem):
         self.__elem = elem
 
+    def get(self):
+        '''
+        If a value is present, returns the value, otherwise raise an Exception.
+
+        :return: the non-null value described by this Optional
+        :raise: Exception if no value is present
+        '''
+        if self.isEmpty():
+            raise Exception("Optional Empty")
+        return self.__elem
+
     def isPresent(self):
+        '''
+        If a value is present, returns true, otherwise false.
+
+        :return: true if a value is present, otherwise false
+        '''
         return not self.isEmpty()
 
     def isEmpty(self):
+        '''
+        If a value is not present, returns true, otherwise false.
+
+        :return: true if a value is not present, otherwise false
+        '''
         return self.__elem is None
 
-    def get(self):
-        if self.isEmpty():
-            raise Exception("Optional Empty")
-        return self.__elem
+    def ifPresent(self, action):
+        '''
+        If a value is present, performs the given action with the value, otherwise does nothing.
+
+        :param Function action: the action to be performed, if a value is present
+        :raise Exception if value is present and the given action is null
+        '''
+        if self.isPresent():
+            action(self.get())
+
+    def ifPresentOrElse(self, action, emptyAction):
+        '''
+        If a value is present, performs the given action with the value, otherwise performs the given empty-based action.
+
+        :param Function action: the action to be performed, if a value is present
+        :param Function emptyAction: the empty-based action to be performed, if no value is present
+        :raise Exception if a value is present and the given action is null, or no value is present and the given empty-based action is null.
+        '''
+        if self.isPresent():
+            action(self.get())
+        else:
+            emptyAction()
+
+    def filter(self, predicate):
+        '''
+        If a value is present, and the value matches the given predicate, returns an Optional describing the value, otherwise returns an empty Optional.
+
+        :param Predicate predicate: the predicate to apply to a value, if present
+        :return: an Optional describing the value of this Optional, if a value is present and the value matches the given predicate, otherwise an empty Optional
+        '''
+        if self.isPresent() and predicate(self.get()):
+            return self
+        else:
+            return Optional.empty()
+
+    def map(self, mapper):
+        '''
+        If a value is present, returns an Optional describing (as if by ofNullable(T)) the result of applying the given mapping function to the value, otherwise returns an empty Optional. 
+        If the mapping function returns a null result then this method returns an empty Optional.
+
+        :param Mapper mapper: the mapping function to apply to a value, if present
+        :return: an Optional describing the result of applying a mapping function to the value of this Optional, if a value is present, otherwise an empty Optional
+        '''
+        if self.isPresent():
+            return Optional.ofNullable(mapper(self.get()))
+        else:
+            return Optional.empty()