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Write example programs and the main demo program
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‎examples/build.gradle

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plugins {
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id 'java'
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id 'application'
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}
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sourceCompatibility = 1.11

‎examples/src/main/java/com/mayankrastogi/cs474/hw2/examples/IteratorExamplesMain.java

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package com.mayankrastogi.cs474.hw2.examples;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import java.util.ArrayList;
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import java.util.Arrays;
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public class IteratorExamplesMain {
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private static final Logger LOGGER = LoggerFactory.getLogger(IteratorExamplesMain.class);
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public static void main(String[] args) {
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System.out.println("\n" +
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"=======================================================================================================\n" +
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" Design Pattern Verifier - Iterator Design Pattern Example Programs\n" +
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"=======================================================================================================\n" +
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"The iterator design pattern \"provides a way to access the elements of an aggregate object sequentially\n" +
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"without exposing its underlying representation.\n" +
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"\n" +
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"This application demonstrates 3 classes that use the iterator pattern and are annotated with different\n" +
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"variations of the @Iterator and @IterableAggregate (and their nested) annotations:\n" +
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"\n" +
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" 1. StudentCollection: A class annotated with @IterableAggregate that implements `java.lang.Iterable`.\n" +
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" It's iterator class is annotated with @Iterator and implements `java.util.Iterator`. The\n" +
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" iterator returns a `Student` object during iteration.\n" +
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" 2. RangeGenerator: A class annotated with @Iterator that generates a primitive `int` value on each\n" +
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" iteration within the range specified while constructing its object.\n" +
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" 3. Tree: A class annotated with @IterableAggregate that provides two methods annotated with\n" +
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" @IteratorFactory. The two methods return instances of `Tree.TreeIterator` that allow the user to\n" +
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" iterate the nodes of the tree in depth-first and breadth-first manners.\n" +
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"======================================================================================================="
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);
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printExampleName("Student Collection Iteration Example");
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runStudentCollectionExample();
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printExampleName("RangeGenerator Iteration Example");
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runRangeExample();
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printExampleName("Tree Iteration Example");
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runTreeExample();
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}
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private static void printExampleName(String exampleName) {
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System.out.println("\n\n" +
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"-------------------------------------------------------------------------------------------------------\n" +
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exampleName + "\n" +
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"-------------------------------------------------------------------------------------------------------\n" +
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"\n"
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);
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}
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private static void runStudentCollectionExample() {
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LOGGER.debug("Creating StudentCollection...");
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var students = new StudentCollection();
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students.addStudent(new Student("Alex", 20, Degree.Bachelors, 3.2f));
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students.addStudent(new Student("Bob", 25, Degree.Masters, 3.6f));
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students.addStudent(new Student("Chuck", 28, Degree.PhD, 3.5f));
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LOGGER.debug("Iterating StudentCollection...");
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for (var student : students) {
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System.out.println("Name: " + student.getName());
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System.out.println("Age: " + student.getAge());
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System.out.println("Degree: " + student.getDegree());
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System.out.println("GPA: " + student.getGPA());
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System.out.println();
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}
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LOGGER.debug("StudentCollection Iteration Example Finished.");
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}
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private static void runRangeExample() {
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int from = 1;
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int to = 10;
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LOGGER.debug(String.format("Creating a RangeGenerator(from: %s, to: %s)...", from, to));
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var range = new RangeGenerator(from, to);
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LOGGER.debug("Iterating RangeGenerator...");
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while (!range.isDone()) {
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System.out.println(range.next());
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}
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LOGGER.debug("RangeGenerator Iteration Example Finished.");
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}
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private static void runTreeExample() {
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System.out.println("" +
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"Sample Tree:\n" +
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"-----------\n" +
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"\n" +
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" 1\n" +
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" _______________________________|_______________________________\n" +
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" | | |\n" +
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" 2 3 4\n" +
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" _______|_______ _______|_______ _______|_______\n" +
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" | | | | | |\n" +
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" 5 6 7 8 9 10\n" +
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"\n");
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LOGGER.debug("Creating 10 nodes using the RangeGenerator...");
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var allNodes = new ArrayList<Node<Integer>>();
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var range = new RangeGenerator(1, 10);
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while (!range.isDone()) {
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allNodes.add(new Node<>(range.next()));
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}
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LOGGER.debug("allNodes: " + allNodes);
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LOGGER.debug("Creating Sample Tree...");
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allNodes.get(0).children = Arrays.asList(allNodes.get(1), allNodes.get(2), allNodes.get(3));
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allNodes.get(1).children = Arrays.asList(allNodes.get(4), allNodes.get(5));
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allNodes.get(2).children = Arrays.asList(allNodes.get(6), allNodes.get(7));
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allNodes.get(3).children = Arrays.asList(allNodes.get(8), allNodes.get(9));
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var tree = new Tree<>(allNodes.get(0));
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LOGGER.debug("tree: " + tree);
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LOGGER.debug("Iterating tree using `dfsIterator()`...");
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System.out.println("Depth-first tree traversal:");
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var iterator = tree.dfsIterator();
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while (!iterator.isDone()) {
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System.out.print(" " + iterator.next().data);
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}
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System.out.println();
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LOGGER.debug("Iterating tree using `bfsIterator()`...");
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System.out.println("Breadth-first tree traversal:");
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iterator = tree.bfsIterator();
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while (!iterator.isDone()) {
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System.out.print(" " + iterator.next().data);
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}
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System.out.println();
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LOGGER.debug("Tree Iteration Example Finished.");
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}
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}

‎examples/src/main/java/com/mayankrastogi/cs474/hw2/examples/RangeGenerator.java

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package com.mayankrastogi.cs474.hw2.examples;
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import com.mayankrastogi.cs474.hw2.annotations.Iterator;
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@Iterator(int.class)
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public class RangeGenerator {
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private final int maxValue;
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private int currentValue;
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public RangeGenerator(int from, int to) {
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this.maxValue = to;
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this.currentValue = from - 1;
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}
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@Iterator.CurrentItem
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public int currentValue() {
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return currentValue;
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}
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@Iterator.IsDone
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public boolean isDone() {
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return currentValue == maxValue;
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}
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@Iterator.NextItem
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public int next() {
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return ++currentValue;
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}
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}

‎examples/src/main/java/com/mayankrastogi/cs474/hw2/examples/StudentCollection.java

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package com.mayankrastogi.cs474.hw2.examples;
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import com.mayankrastogi.cs474.hw2.annotations.IterableAggregate;
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import com.mayankrastogi.cs474.hw2.annotations.Iterator;
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import java.util.ArrayList;
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import java.util.NoSuchElementException;
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enum Degree {
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Bachelors,
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Masters,
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PhD
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}
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@IterableAggregate(StudentCollection.StudentCollectionIterator.class)
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public class StudentCollection implements Iterable<Student> {
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private ArrayList<Student> studentsList = new ArrayList<>();
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public void addStudent(Student student) {
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studentsList.add(student);
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}
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public void removeStudent(Student student) {
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studentsList.remove(student);
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}
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@Override
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@IterableAggregate.IteratorFactory
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public java.util.Iterator<Student> iterator() {
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return new StudentCollectionIterator();
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}
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@Iterator(Student.class)
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public class StudentCollectionIterator implements java.util.Iterator<Student> {
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private int currentIndex;
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private StudentCollectionIterator() {
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currentIndex = -1;
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}
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@Iterator.CurrentItem
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public Student current() {
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return currentIndex < 0 ? null : studentsList.get(currentIndex);
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}
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@Override
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@Iterator.IsDone
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public boolean hasNext() {
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return currentIndex < studentsList.size() - 1;
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}
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@Override
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@Iterator.NextItem
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public Student next() {
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if (hasNext()) {
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currentIndex++;
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return current();
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} else {
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throw new NoSuchElementException("StudentCollectionIterator has finished iterating over all the students in the collection");
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}
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}
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}
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}
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class Student {
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private String name;
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private int age;
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private Degree degree;
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private float gpa;
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public Student(String name, int age, Degree degree, float gpa) {
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this.name = name;
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this.age = age;
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this.degree = degree;
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this.gpa = gpa;
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}
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public String getName() {
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return name;
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}
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public int getAge() {
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return age;
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}
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public Degree getDegree() {
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return degree;
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}
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public float getGPA() {
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return gpa;
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}
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}

‎examples/src/main/java/com/mayankrastogi/cs474/hw2/examples/Tree.java

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package com.mayankrastogi.cs474.hw2.examples;
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import com.mayankrastogi.cs474.hw2.annotations.IterableAggregate;
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import com.mayankrastogi.cs474.hw2.annotations.Iterator;
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import java.util.ArrayDeque;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.NoSuchElementException;
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@IterableAggregate(Tree.TreeIterator.class)
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public class Tree<T> {
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private Node<T> root;
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public Tree(Node<T> root) {
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this.root = root;
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}
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@IterableAggregate.IteratorFactory
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public TreeIterator dfsIterator() {
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return new TreeIterator(true);
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}
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@IterableAggregate.IteratorFactory
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public TreeIterator bfsIterator() {
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return new TreeIterator(false);
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}
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@Override
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public String toString() {
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return "Tree(root: " + root + ")";
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}
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@Iterator(Node.class)
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public class TreeIterator {
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private boolean dfs;
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private Node<T> currentNode;
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private ArrayDeque<Node<T>> deque;
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private TreeIterator(boolean dfs) {
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this.dfs = dfs;
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deque = new ArrayDeque<>();
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deque.add(root);
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}
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@Iterator.CurrentItem
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public Node<T> currentNode() {
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return currentNode;
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}
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@Iterator.IsDone
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public boolean isDone() {
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return deque.isEmpty();
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}
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@Iterator.NextItem
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public Node<T> next() {
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if (isDone()) throw new NoSuchElementException("All nodes in the tree have been traversed.");
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currentNode = deque.pop();
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if (dfs) {
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var childrenIterator = currentNode.children.listIterator(currentNode.children.size());
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while (childrenIterator.hasPrevious()) {
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deque.push(childrenIterator.previous());
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}
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} else {
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deque.addAll(currentNode.children);
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}
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return currentNode();
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}
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}
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}
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class Node<T> {
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T data;
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List<Node<T>> children;
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public Node(T data) {
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this.data = data;
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this.children = new ArrayList<>();
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}
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@Override
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public String toString() {
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return "Node(data: " + data + ", children: " + children + ")";
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}
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}

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