Iterable Immutable List Assignment

Studio To Revisit

In this studio we will complete the DefaultImmutableList implementation from the ImmutableList studio.

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