CODEWITHSUNDEEP
javajava-stream
Gavin
Gavin

Reputation: 1767

Java Streams, skipping the first item in each list in a Stream of List of elements

I have a number of input tables in a list, each input table has a header row which I would like to ignore.

Minimal example:

List<String> a = Arrays.asList("header", "v1", "v2", "v3");
List<String> b = Arrays.asList("header", "a1", "a2");
List<String> c = Arrays.asList("header", "b1", "b2", "b3", "b4");

List<List<String>> data = Arrays.asList(a, b, c);

List<String> result = data.stream()
    .map(t -> t.subList(1, t.size()))
    .flatMap(List::stream)
    .collect(Collectors.toList());

Is there a "nicer" way to skip the header row then using map on each table?

Note: I am using Java 8 and unable to migrate to a newer JDK

Upvotes: 2

Views: 2047

Answers (3)

Vikas
Vikas

Reputation: 7165

One more possible way is to use filter as below,

List<String> result = data.stream()
    .flatMap(List::stream)
    .filter(e->!e.equals("header"))
    .collect(Collectors.toList());

Upvotes: 0

ernest_k
ernest_k

Reputation: 45319

You can either call stream on the the result of subList():

List<String> result = data.stream()
    .flatMap(t -> t.subList(1, t.size()).stream())
    .collect(Collectors.toList());

Or, alternatively, call skip on the inner stream:

List<String> result = data.stream()
    .flatMap(l -> l.stream().skip(1))
    .collect(Collectors.toList());

Upvotes: 2

Eran
Eran

Reputation: 393831

Use skip():

List<String> result = data.stream()
    .flatMap(t -> t.stream().skip(1))
    .collect(Collectors.toList());

Upvotes: 6

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