Iterable Immutable List Assignment

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Code To Implement

DefaultImmutableList

class: DefaultImmutableList.java Java.png
methods: head
tail
isEmpty
iterator
package: immutable.list.assignment
source folder: src/main/java

default constructor

head and tail constructor

head

tail

isEmpty

iterator

Lists

Lists is a class which holds a number of static methods. As we know, in the Kingdom of Nouns, Verbs must always have an escort.

The first two static methods nil and cons will each call a constructor of the DefaultImmutableList class. The third method brackets will use nil and cons to build up the desired ImmutableList.

class: Lists.java Java.png
methods: nil
cons
brackets
package: immutable.list.assignment
source folder: src/main/java

nil

public static <E> ImmutableList<E> nil()

Analogous to the SML List nil constructor.

Note: often SML programs use empty brackets [] instead of nil.

cons

public static <E> ImmutableList<E> cons(E head, ImmutableList<E> tail)

Analogous to the SML List :: constructor.

brackets

@SafeVarargs
public static <E> ImmutableList<E> brackets(E... elements)

brackets accepts variable length arguments as specified by the ... syntax. When implementing the brackets method you can treat elements as an array. Combining generics and varargs https://stackoverflow.com/questions/14231037/java-safevarargs-annotation-does-a-standard-or-best-practice-exist can be problematic] if the implementation lets the E[] escape since it will actually be an Object[]. The @SafeVarargs annotation indicates a promise that you will rely only on the elements of the array being of type E and not the array being of type E[]. This should not be a problem since you should not require any unsafe use of varargs.

Note: be sure to cons the elements on from the back of the elements array to the front.

Performance

The code:

ImmutableList<Integer> numbers = Lists.brackets(4, 66, 99);
for (int i : numbers) {
	System.out.println(i);
}

produces:

4
66
99

Test

class: ListsTestSuite.java Junit.png
package: immutable.list.assignment
source folder: src/test/java