Java compare two lists of String of same size where order is important

Question

I am currently stuck while comparing two list of strings. Here are the inputs:

First list : three, two, ten, five.
Second list: three, ten, two, five.

The order is important in both list in such a way that: if one element index is not same in other list, then it should put an empty line.

I have attached a screen shot for better clarity.

Here is my code

public static void main(String[] args) {

 List<String> list1 = new ArrayList<String>();
 List<String> list2 = new ArrayList<String>();


    list1.add("three");
    list1.add("two");
    list1.add("ten");
    list1.add("five");

    list2.add("three");
    list2.add("ten");
    list2.add("two");
    list2.add("five");

    for(int iIndex = 0, jIndex = 0; iIndex < list1.size() && jIndex < list2.size(); iIndex ++, jIndex++) {
        if(!list1.get(iIndex).contentEquals(list2.get(jIndex))) {
            list1.add(jIndex, "");
        }
    }

Note: I have searched and checked each listed topics before posting this question. Thank you for your help

Answer 1

If I understood your question correctly you need something like this

int size = list2.size();
for(int i = 0; i < size ; i++) {
    if(!list1.get(i).contentEquals(list2.get(i))) {
      if(list2.size() <= list1.size()) {
        list2.add(i, "XXX");
        size +=1;
      } else {
        list1.add(i, "XXX");
      } 
    }
}

And the output will be:

three   three
two     XXX
ten     ten
XXX     two
five    five

I've added XXX to view them easier. You should also check the case when the lists are not equal in size since it might change the expected output of your program.

UPDATE:

You can try to do something like this.

int size = list1.size();
for(int i = 0; i < size; i++) {
  if(list1.size() == i){
    list1.add(i, "XXX");
    continue;
  }
  if(list2.size() == i){
    list2.add(i, "XXX");
    continue;
  }
  if(!list1.get(i).contentEquals(list2.get(i))) {
    int next_index1 = list2.subList(i, list2.size()).indexOf(list1.get(i));
    int next_index2 = list1.subList(i, list1.size()).indexOf(list2.get(i));

    if (next_index1 == -1){
      list2.add(i, "XXX");
    }
    else if(next_index2 == -1){
      list1.add(i, "XXX");
    } 
    else if(next_index1 < next_index2) {
      list1.add(i, "XXX");
    } else {
      list2.add(i, "XXX");
    } 
  }
  size = list1.size() < list2.size() ? list2.size() : list1.size();
}
for(int i = 0; i < size ; i++) {
  System.out.println(list1.get(i) + "   " + list2.get(i));
}

In brief, it will check when is the closest occurrence of a string in the other list. For example if your lists are:

three   three
two     ten
ten     two
five    five

After the first elements in each list, because they are the same, it will find the distance between the current position in the first list and the index of the first occurrence of that element in the second list and the other way around. If the distances are equal then it will add space in the second list. So the result will be

three   three
two     XXX
ten     ten
XXX     two
five    five

But if your list are

three   three
two     ten
five     two

the output will be

three   three
XXX     ten
two     two
five    XXX