pick first N elements from a static list java

Question

I want to pick first N elements from a list in java

String[] ligature = new String{there,is not,a,single,person,who,knows,the,answer};

Now I want to pick first 5 elements from this.something like

Stiring[] selectedLigature = ligature[0:4];

I want to do it without using for loop.

Why? Better use `List`. You could do: `Arrays.asList(ligature).subList( 0,5 ).toArray()`; But that is cumbersome. — Rob Audenaerde, Aug 15 '18 at 08:41
@RobAu `.toArray(new String[5])` would be needed if one wants to get a typed array back — Lino, Aug 15 '18 at 08:45
@Lino that is silly. You just need `toArray(new String[0])` as the argument is only used to determine the type. — Rob Audenaerde, Aug 15 '18 at 08:48
@RobAu if the length of the input array is equal or bigger than the `List` then it is used. At least in the case of `ArrayList`. — Lino, Aug 15 '18 at 08:50
@Lino. Didn't know! It also sets elements in given array to `null` if it is bigger. Thanks! — Rob Audenaerde, Aug 15 '18 at 08:53
@Lino is should *always* be `new String[0]` without an actual size https://stackoverflow.com/questions/51766615/list-to-varargs-with-pre-difined-size-or-without-size/51775139#51775139 — Eugene, Aug 15 '18 at 09:11

Eugene · Answer 1 · 2018-08-15T08:56:12.513

9

Do not stream this simple case, there is subList for this:

// for a List
yourList.subList(0, 5)...

// for an array
Arrays.copyOfRange

edited Aug 15 '18 at 08:56

answered Aug 15 '18 at 08:45

Eugene

Agreed. `subList` is almost always better, but tricky as you can modify the original list by accident as it is just a view on the `List`. – Rob Audenaerde Aug 15 '18 at 08:46
@RobAu `Arrays.copyOfRange` for such a case – Eugene Aug 15 '18 at 08:47
@Eugene `Collections.unmodifiableList` will return an list that cannot be modified. Arrays.copyOfRange will also not deep-copy the elements inside? – Rob Audenaerde Aug 15 '18 at 08:55
@RobAu you right, me wrong, `System.arrayCopy` does not do a deep copy. – Eugene Aug 15 '18 at 09:05

Jack Flamp · Answer 2 · 2018-08-15T08:50:47.380

3

Arrays class has a method for this:

Arrays.copyOfRange(ligature, 0, 5);

edited Aug 15 '18 at 08:50

answered Aug 15 '18 at 08:45

Jack Flamp

2 Answers2