Created
November 23, 2016 19:33
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List of Lists iterator.
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package collections; | |
import java.util.Arrays; | |
import java.util.List; | |
/** | |
* Created by amit.saurav on 11/23/16. | |
*/ | |
public class ListOfLists <T> { | |
private final List<List<T>> listOfLists; | |
private int currentRow; | |
private int currentCol; | |
public ListOfLists(List<List<T>> lists) { | |
listOfLists = lists; | |
resetIterator(); | |
} | |
public void resetIterator() { | |
currentCol = currentRow = 0; | |
} | |
public boolean hasNext() { | |
// Not enough elements left | |
if (currentRow == listOfLists.size() - 1) { | |
return false; | |
} | |
// Definitely more elements left in the current list | |
if (listOfLists.get(currentRow).size() > currentCol + 1) { | |
return true; | |
} | |
return getNextNonEmptyList() == -1 ? false : true; | |
} | |
public T next() { | |
if (!hasNext()) { | |
return null; | |
} | |
// Definitely more elements left in the current list | |
if (listOfLists.get(currentRow).size() > currentCol) { | |
return listOfLists.get(currentRow).get(currentCol++); | |
} | |
currentRow = getNextNonEmptyList(); | |
if (currentRow == -1) { | |
resetIterator(); | |
return null; | |
} else { | |
currentCol = 0; | |
return listOfLists.get(currentRow).get(currentCol++); | |
} | |
} | |
private int getNextNonEmptyList() { | |
int tempRow = currentRow; | |
while (tempRow < listOfLists.size() - 1 && listOfLists.get(++tempRow).size() == 0); | |
if (tempRow == listOfLists.size() - 1) { | |
return -1; | |
} else { | |
return tempRow; | |
} | |
} | |
public static void main(String[] args) { | |
List<Integer> list1 = Arrays.asList( 1, 2, 3, 4, 5); | |
List<Integer> list2 = Arrays.asList( 6, 7, 8, 9); | |
List<Integer> list3 = Arrays.asList(10, 11, 12); | |
List<Integer> list4 = Arrays.asList(13, 14); | |
List<Integer> list5 = Arrays.asList(15); | |
List<Integer> list6 = Arrays.asList(); | |
List<Integer> list7 = Arrays.asList(); | |
List<Integer> list8 = Arrays.asList(16); | |
List<Integer> list9 = Arrays.asList(); | |
List<List<Integer>> lists = Arrays.asList(list1, list2, list3, list4, list5, list6, list7, list8, list9); | |
ListOfLists<Integer> subject = new ListOfLists<>(lists); | |
while (subject.hasNext()) { | |
System.out.print(subject.next() + ", "); | |
} | |
System.out.println(); | |
} | |
} |
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