Dorothy's Fears

AnimalsIterator.java

package oz;

import java.util.Iterator;

public class AnimalsIterator implements Iterator<String> {

	private String[] animals;
	int index; // defaults to zero
	
	public AnimalsIterator(String... animals) {
		this.animals = animals;
	}

	@Override
	public String next() {
		// you would usually see this as:
		//	return animals[index++];
		String currentAnimal = animals[index];
		index++;
		return currentAnimal;
	}

	@Override
	public boolean hasNext() {
		return index < animals.length;
	}

}

AnimalsIteratorTest.java

package oz;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.util.Iterator;

import org.junit.Assert;
import org.junit.Test;

public class AnimalsIteratorTest {

	@Test
	public void shouldReturnTheFirstElement() {
		// arrange
		AnimalsIterator underTest = new AnimalsIterator("Lions");
		// act
		String result = underTest.next();
		// assert
		assertEquals("Lions", result);
	}
	
	@Test
	public void shouldReturnSecondElement() {
		String[] animals = { "Lions", "Tigers" };
		AnimalsIterator underTest = new AnimalsIterator(animals);
		underTest.next(); // Lions
		String result = underTest.next();
		assertEquals("Tigers", result);
	}
	
	@Test
	public void shouldHaveNext() { /// start with the positive case
		AnimalsIterator underTest = new AnimalsIterator("Ducks");
		boolean result = underTest.hasNext();
		assertTrue(result);
	}
	
	@Test
	public void shouldNotHaveNext() {
		AnimalsIterator underTest = new AnimalsIterator();
		boolean result = underTest.hasNext();
		assertFalse(result);
	}
	
	@Test
	public void shouldBeAnIterator() {
		AnimalsIterator underTest = new AnimalsIterator();
		boolean isAnIterator = (underTest instanceof Iterator);
		assertTrue(isAnIterator);
	}
}

DorothysFears.java

package oz;

import java.util.Iterator;

public class DorothysFears implements Iterable<String> {

	private String[] fears = { "Lions", "Tigers", "Bears" };
	
	@Override
	public Iterator<String> iterator() {
		return new AnimalsIterator(fears);
	}

}

OzApp.java

package oz;

public class OzApp {

	public static void main(String[] args) {
		
		DorothysFears fears = new DorothysFears();
		
		System.out.println("Dorothy's fears are");
		for(String f: fears) {
			System.out.println(f);
		}
		System.out.println("Oh my.");
	}
}