Merge each element of multiple lists into one Element and return another list in java 8

Question

for simplicity I have 2 lists of String and I need to join the strings into one and create another list. For eg --

List 1 = [a,b,c,d]
List 2 = [e,f,g,h]

I want the output as

List3 = [ae,bf,cg,dh]

I can do this using regular for loops. but dont know how to proceed for java8

I am trying to get myself thinking in n Java 8 :-)

So you're looking for a [zip](http://hackage.haskell.org/package/base-4.10.0.0/docs/Prelude.html#v:zip) operation? — Andy Turner, Sep 29 '17 at 21:32
Duplicated of https://stackoverflow.com/questions/189559/how-do-i-join-two-lists-in-java The second answer shows an example for Java 8 — Rafa, Sep 29 '17 at 21:35
@Rafa no, that's concatenating the two lists, which isn't what OP is asking. — Andy Turner, Sep 29 '17 at 21:36
yes.. I am looking for zip operation.. didnt know there was a term for that :-) Thanks Andy.. — Roma, Sep 29 '17 at 21:39

Andy Turner · Answer 1 · 2017-09-29T21:58:37.413

3

I'm not sure there's a better (easy) way to do this than to access the elements from the two lists by index:

List<String> zipped = IntStream.range(0, list.size())
    .mapToObj(i -> list1.get(i) + list2.get(i))
    .collect(Collectors.toList());

edited Sep 29 '17 at 21:58

answered Sep 29 '17 at 21:34

Andy Turner

can I add another list after zipping the first two lists into one before collecting into a list? – Roma Sep 30 '17 at 05:22
1

You haven't mentioned in this code, what `list` is. Also, this will throw `java.lang.IndexOutOfBoundsException` if `list.size()` is greater than the size of `list1` or that of `list2`. – Arvind Kumar Avinash Feb 09 '21 at 10:42

1 Answers1