Concatenate Vectors in Java

Question

Is there any easy and quick way to merge 2 java vectors to 1?

For example if I have:

  Vector<Object> Va = (Vector<Object>)Return_Vector_with_Objs();
  Vector<Object> Vb = (Vector<Object>)Return_Vector_with_Objs();

  Vector<Object> Vmerge_a_b = function_that_takes_a_b_merges(Va,Vb);

Is there any function like function_that_takes_a_b_merges or easy way to merge these 2 vectors ?

I don't want to do it with loops and add() etc. I am asking if there is a quicker way.

EDIT: I also want the repeated objects to be ruled out.

I'd read up on vector addition firstly: http://www.physicsclassroom.com/class/vectors/u3l1b.cfm — , Feb 06 '13 at 19:55
Depends on your definition of _merging_. You can use `Vector#addAll`, a `TreeSet` if you want orderer unrepeated elements, an `ArrayList` or even a `LinkedList`. What's merging for you? the elements of vector1 followed by the elements of vector2?. — Fritz, Feb 06 '13 at 19:57
That is a good comment. I actually want a new vector with all the unrepeated objects. I don't care about ordering at all (but just for curiosity how could it be ordered?!) — , Feb 06 '13 at 20:02
Possible duplicate of [How to zip two Java Lists](https://stackoverflow.com/questions/31963297/how-to-zip-two-java-lists) — tkruse, Jan 25 '18 at 04:32

score 6 · Answer 1 · answered Feb 06 '13 at 20:00

6

Sure!

static Vector<Object> function_that_takes_a_b_merges(Vector<Object> Va, Vector<Object> Vb) {
  Vector<Object> merge = new Vector<Object>();
  merge.addAll(Va);
  merge.addAll(Vb);
  return merge;
}

It’s important to start with a new vector, otherwise you will change Va if you call Va.addAll().

answered Feb 06 '13 at 20:00

andrewdotn

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Why wouldn't just saying Va.addAll(Vb) in the first place be a good idea? Would that not work? – BreadicalMD Mar 25 '14 at 15:12
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@BreadicalMD “It’s important to start with a new vector, otherwise you will change `Va` if you call `Va.addAll()`.” – andrewdotn Mar 25 '14 at 17:04

Reimeus · Answer 2 · 2013-02-06T20:27:55.603

3

You could do:

Set<String> set = new HashSet<>(va);
set.addAll(vb);
Vector<String> merged = new Vector<>(set);

Note:Vector is quite an old Collection now which has the overhead of synchronized methods which has a performance cost. ArrayList could be used instead and also has the addAll method from the List interface contract. If you do require a synchronized Collection, you can use Collections.synchronizedList to synchronize your original List.

edited Feb 06 '13 at 20:27

answered Feb 06 '13 at 19:56

Reimeus

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I actually wanted to have a synchronized collection that's why I used it. So there will be repeated object in mergedVector with this method? – Feb 06 '13 at 20:03
I think you are looking for something like a `HashSet` in that case. – Reimeus Feb 06 '13 at 20:11
Vector is still actual for such old but popular libraries as JSCH, for lsEntry class, for example. – Zon Oct 31 '13 at 17:03

Concatenate Vectors in Java

2 Answers2