Iterable Immutable List Assignment

Exercise To Revisit

In this studio we will complete the EmptyImmutableList and NonEmptyImmutableList implementations from the ImmutableList exercise.

ImmutableList

The ImmutableList interface extends Iterable which has one method: iterator().

public interface ImmutableList<E> extends Iterable<E> {
	E head();
	ImmutableList<E> tail();
	boolean isEmpty();
}

Iterable

interface java.lang.Iterable<T>

1. Iterator<T> iterator()

Iterator

interface java.util.Iterator<T>

1. boolean hasNext()
2. T next()

Example

class:	IterableImmutableListExample.java
package:	immutable.list.example
source folder:	src/main/java

The code:

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

produces:

4
66
99

Diagrams

ImmutableList

ImmutableList<Char> letters = Lists.brackets('A', 'B', 'C'); 

Initial Iterator State

ImmutableList<Char> letters = Lists.brackets('A', 'B', 'C');
Iterator<Char> iter = letters.iterator(); 

Iterator State after next()

ImmutableList<Char> letters = Lists.brackets('A', 'B', 'C');
Iterator<Char> iter = letters.iterator();
if(iter.hasNext()) {
    char a = iter.next();
} 

Iterator State after next() next()

ImmutableList<Char> letters = Lists.brackets('A', 'B', 'C');
Iterator<Char> iter = letters.iterator();
if(iter.hasNext()) {
    char a = iter.next();
    if(iter.hasNext()) {
        char b = iter.next();
    }
} 

Iterator State after next() next() next()

ImmutableList<Char> letters = Lists.brackets('A', 'B', 'C');
Iterator<Char> iter = letters.iterator();
if(iter.hasNext()) {
    char a = iter.next();
    if(iter.hasNext()) {
        char b = iter.next();
        if(iter.hasNext()) {
            char c = iter.next();
        }
    }
} 

Code To Implement

enum EmptyImmutableList

class:	EmptyImmutableList.java
methods:	iterator
package:	immutable.list.assignment
source folder:	src/main/java

iterator()

return an Iterator for the EmptyImmutableList.

Question to ask yourself: Does an iterator for an EmptyImmutableList ever have a next?

class NonEmptyImmutableList

class:	NonEmptyImmutableList.java
methods:	iterator
package:	immutable.list.assignment
source folder:	src/main/java

iterator()

return an Iterator for this instance of NonEmptyImmutableList.

Note: If you are within an anonymous inner class, the way to get the outer class's this instance is to qualify it with the out class identifier. For example:

NonEmptyImmutableList.this

Test

class:	IterableAssignmentTestSuite.java
package:	immutable.list.assignment
source folder:	src/test/java

class:	ImmutableListIteratorMethodTestSuite.java
package:	immutable.list.assignment
source folder:	src/test/java