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deepika087/GenericMultiListIterator.java

Last active June 11, 2018 15:29
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Iterates through (generic) List of List <<a1,a2>, <b1,b2,b3,b4>, <c1,c2,c3,c4,c5,c6,c7>> Generates output a1, b1, c1, a2, b2, c2, b3, c3, b4, c4,c5,c6,c7
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GenericMultiListIterator.java
package com.expedia.sample;
import java.util.ArrayList;
import java.util.Iterator;
public class MultiListIterator<E> implements Iterator<E> {
private ArrayList<ArrayList<E>> useThisList;
private int numOfList;
private int[] sizeOfEachList;
private int[] prevReturnedOfEachList;
private int lastRetList;
private int lastRetIndex;
public MultiListIterator(ArrayList<ArrayList<E>> myList) {
this.useThisList = myList;
numOfList = myList.size();
sizeOfEachList = new int[numOfList];
prevReturnedOfEachList = new int[numOfList];
for (int i = 0; i < numOfList; i++) {
sizeOfEachList[i] = myList.get(i).size();
prevReturnedOfEachList[i] = -1;
}
lastRetList = -1;
lastRetIndex = -1;
}
public boolean hasNext() {
int currentListIndex = lastRetList;
int currentIndex = -1;
int count = -1;
do {
currentListIndex = (currentListIndex + 1) % numOfList;
currentIndex = prevReturnedOfEachList[currentListIndex] + 1;
count++;
}while(currentIndex == sizeOfEachList[currentListIndex] && count < numOfList);
if (count == numOfList) {
//System.out.println("False: Checked for currentList = " + currentListIndex + " and currentIndex = " + currentIndex);
return false;
}
if ( currentIndex < sizeOfEachList[currentListIndex]) {
//System.out.println("True : Checked for currentList = " + currentListIndex + " and currentIndex = " + currentIndex);
return true;
}
return false;
}
public E next() {
int currentListIndex = lastRetList;
int currentIndex = -1;
int count = -1;
do {
currentListIndex = (currentListIndex + 1) % numOfList;
currentIndex = prevReturnedOfEachList[currentListIndex] + 1;
count++;
} while(currentIndex == sizeOfEachList[currentListIndex] && count < numOfList);
if (count == numOfList) {
//System.out.println("Cann't Return: Checked for currentList = " + currentListIndex + " and currentIndex = " + currentIndex);
return null;
}
if ( currentIndex < sizeOfEachList[currentListIndex]) {
//System.out.println("Returning : Checked for currentList = " + currentListIndex + " and currentIndex = " + currentIndex);
lastRetList = currentListIndex;
lastRetIndex = currentIndex;
E temp = this.useThisList.get(lastRetList).get(lastRetIndex);
prevReturnedOfEachList[lastRetList] = lastRetIndex;
return temp;
}
return null;
}
public static void main(String[] args) {
ArrayList<String> list1 = new ArrayList<String>();
list1.add("a1");
list1.add("a2");
ArrayList<String> list2 = new ArrayList<String>();
list2.add("b1");
list2.add("b2");
list2.add("b3");
list2.add("b4");
ArrayList<String> list3 = new ArrayList<String>();
list3.add("c1");
list3.add("c2");
list3.add("c3");
list3.add("c4");
list3.add("c5");
list3.add("c6");
ArrayList<ArrayList<String>> finalList = new ArrayList<ArrayList<String>>();
finalList.add(list1);
finalList.add(list2);
finalList.add(list3);
MultiListIterator itr = new MultiListIterator<String>(finalList);
itr.hasNext();
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
System.out.println(itr.next());
ArrayList<Integer> list21 = new ArrayList<Integer>();
list21.add(1);
list21.add(2);
ArrayList<Integer> list22 = new ArrayList<Integer>();
list22.add(3);
list22.add(4);
list22.add(5);
list22.add(6);
ArrayList<Integer> list23 = new ArrayList<Integer>();
list23.add(7);
list23.add(8);
list23.add(9);
list23.add(10);
list23.add(11);
list23.add(12);
ArrayList<ArrayList<Integer>> finalList1 = new ArrayList<ArrayList<Integer>>();
finalList1.add(list21);
finalList1.add(list22);
finalList1.add(list23);
System.out.println("Intger list");
MultiListIterator itr1 = new MultiListIterator<Integer>(finalList1);
itr1.hasNext();
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
System.out.println(itr1.next());
}
}
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