CODEWITHSUNDEEP
javacollectionsiteration
Evgeny Kharitonov
Evgeny Kharitonov

Reputation: 1107

Preferred way to iterate a List except the first element

I often need to iterate through a List starting at the second element. For example here is a column:

List<String> column = Arrays.asList("HEADER", "value1", "value2", "value3");

I need to print only values.

I see three approaches:

  1. Using sublist:

    for (String s : column.subList(1, column.size())) {
    System.out.println(s);
}

  2. Using ListIterator

    for (ListIterator<String> iter = column.listIterator(1); iter.hasNext(); ) {
    System.out.println(iter.next());
}

  3. Using index

    for (int i = 1; i < column.size(); i++) {
    System.out.println(column.get(i));
}

What is the most preferred one considering readability, best practices and performance?

In my opinion sublist solution is more readable, but I rarely saw it in practice. Does it have any significant deficiencies comparing to index solution?

Upvotes: 16

Views: 10435

Answers (3)

GhostCat
GhostCat

Reputation: 140457

This really boils down to (almost) "personal style" only.

You should simply pick what works best for you/your team.

Option 3 seems to be the one that comes with the least overhead - options 1 and 2 both create new "intermediate" objects (the sublist respectively the iterator). And just to be precise: sublist() doesn't create a new list and populate that - it boils down to a new Sublist object that simply "knows" about the boundaries within the larger parent list.

But: as soon as we consider lists that are not supporting random access to list elements (think linked lists for example) then option 3 results in a lot of performance cost compared to the others.

Upvotes: 5

zaerymoghaddam
zaerymoghaddam

Reputation: 3127

It's more a matter of personal preferences. The sublist method doesn't return a new object, just a view on top of the current list, so it doesn't have any memory overhead. I think the readability is the only criteria to decide about this and the last option is the most readable solution and doesn't need to call any extra method (e.g. iterator, sublist, etc.)

Upvotes: 1

senjin.hajrulahovic
senjin.hajrulahovic

Reputation: 3191

If you use Java 8 or above you can use:

column.stream().skip(1).forEach((c) -> System.out.println(c))

Upvotes: 14

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