List and array iterators for iterating over a matrix

ArrayMatrixIterator.java

import java.util.Iterator;
import java.util.NoSuchElementException;

import com.google.common.base.Preconditions;

/**
 * Provides data from a matrix represented using a 2D array
 * 
 * @author Dhwaneet Bhatt
 * @since Aug 17, 2016
 */
public class ArrayMatrixIterator<T> implements Iterator<T> {

  private T[][] dataset;
  private int rowIndex;
  private int columnIndex;

  public ArrayMatrixIterator(T[][] dataset) {
    Preconditions.checkNotNull(dataset);
    this.dataset = dataset;
  }

  @Override
  public boolean hasNext() {
    if (rowIndex >= dataset.length)
      return false;
    if (columnIndex >= dataset[rowIndex].length &&
        (rowIndex >= dataset.length || rowIndex == dataset.length - 1))
      return false;
    return true;
  }

  @Override
  public T next() {
    if (!hasNext())
      throw new NoSuchElementException();
    if (columnIndex >= dataset[rowIndex].length) {
      rowIndex++;
      columnIndex = 0;
    }
    return dataset[rowIndex][columnIndex++];
  }

  @Override
  public void remove() {
    throw new UnsupportedOperationException("Not yet implemented");
  }

}

ArrayMatrixIteratorTest.java

import java.util.NoSuchElementException;

import org.testng.Assert;
import org.testng.annotations.Test;

/**
 * @author Dhwaneet Bhatt
 * @since Aug 17, 2016
 */
public class ArrayMatrixIteratorTest {
  
  @Test
  public void testGetData() {
    String[] row1 = {"0", "1", "2", "3"};
    String[] row2 = {"4", "5", "6", "7"};
    String[] row3 = {"8", "9", "10", "11"};
    String[] row4 = {"12", "13", "14", "15"};
    String[][] dataset = {row1, row2, row3, row4};
    ArrayMatrixIterator<String> provider = new ArrayMatrixIterator<>(dataset);
    int i = 0;
    while (provider.hasNext()) {
      String data = provider.next();
      Assert.assertNotNull(data);
      Assert.assertEquals(Integer.parseInt(data), i++);
    }
    Assert.assertFalse(provider.hasNext());
  }
  
  @Test(expectedExceptions = NoSuchElementException.class)
  public void testNoSuchElementException() {
    String[] row1 = {"0"};
    String[] row2 = {"1"};
    String[][] dataset = {row1, row2};
    ArrayMatrixIterator<String> provider = new ArrayMatrixIterator<>(dataset);
    Assert.assertEquals(provider.next(), "0");
    Assert.assertEquals(provider.next(), "1");
    Assert.assertFalse(provider.hasNext());
    provider.next();
  }

  @Test(expectedExceptions = NoSuchElementException.class)
  public void testReturnFalseForEmptyDataset() {
    String[][] dataset = new String[0][0];
    ArrayMatrixIterator<String> provider = new ArrayMatrixIterator<>(dataset);
    Assert.assertFalse(provider.hasNext());
    provider.next();
  }

}

ListMatrixIterator.java

import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

import com.google.common.base.Preconditions;

/**
 * Provides data from a matrix represented using nested lists of depth 2
 * 
 * @author Dhwaneet Bhatt
 * @since Aug 17, 2016
 */
public class ListMatrixIterator<T> implements Iterator<T> {

  private List<List<T>> dataset;
  private Iterator<List<T>> rowIterator;
  private Iterator<T> columnIterator;

  public ListMatrixIterator(List<List<T>> dataset) {
    Preconditions.checkNotNull(dataset);
    this.dataset = dataset;
    this.rowIterator = dataset.iterator();
  }
  
  private boolean noDataInColumn() {
    return this.columnIterator == null || !this.columnIterator.hasNext();
  }

  @Override
  public boolean hasNext() {
    if (this.dataset.isEmpty())
      return false;
    if (noDataInColumn())
      return this.rowIterator.hasNext();
    return this.columnIterator.hasNext();
  }

  @Override
  public T next() {
    if (!hasNext())
      throw new NoSuchElementException();
    if (noDataInColumn()) {
      this.columnIterator = this.rowIterator.next().iterator();
    }
    return this.columnIterator.next();
  }

  @Override
  public void remove() {
    throw new UnsupportedOperationException("Not yet implemented");
  }

}

ListMatrixIteratorTest.java

import java.util.List;
import java.util.NoSuchElementException;

import org.testng.Assert;
import org.testng.annotations.Test;

import com.google.common.collect.Lists;

/**
 * @author Dhwaneet Bhatt
 * @since Aug 17, 2016
 */
@SuppressWarnings("unchecked")
public class ListMatrixIteratorTest {

  @Test
  public void testGetData() {
    List<String> row1 = Lists.newArrayList("0", "1", "2", "3");
    List<String> row2 = Lists.newArrayList("4", "5", "6", "7");
    List<String> row3 = Lists.newArrayList("8", "9", "10", "11");
    List<String> row4 = Lists.newArrayList("12", "13", "14", "15");
    List<List<String>> dataset = Lists.newArrayList(row1, row2, row3, row4);
    ListMatrixIterator<String> provider = new ListMatrixIterator<>(dataset);
    int i = 0;
    while (provider.hasNext()) {
      String data = provider.next();
      Assert.assertNotNull(data);
      Assert.assertEquals(Integer.parseInt(data), i++);
    }
    Assert.assertFalse(provider.hasNext());
  }

  @Test(expectedExceptions = NoSuchElementException.class)
  public void testNoSuchElementException() {
    List<String> row1 = Lists.newArrayList("0");
    List<String> row2 = Lists.newArrayList("1");
    List<List<String>> dataset = Lists.newArrayList(row1, row2);
    ListMatrixIterator<String> provider = new ListMatrixIterator<>(dataset);
    Assert.assertEquals(provider.next(), "0");
    Assert.assertEquals(provider.next(), "1");
    Assert.assertFalse(provider.hasNext());
    provider.next();
  }

  @Test(expectedExceptions = NoSuchElementException.class)
  public void testReturnFalseForEmptyDataset() {
    List<List<String>> dataset = Lists.newArrayList();
    ListMatrixIterator<String> provider = new ListMatrixIterator<>(dataset);
    Assert.assertFalse(provider.hasNext());
    provider.next();
  }

}