CODEWITHSUNDEEP
javaarrayslistarraylist2d
BoJack Horseman
BoJack Horseman

Reputation: 169

Index of an element in a 2D ArrayList Java

I have a 2D ArrayList (ArrayList within an ArrayList). For instance, I have the following values for it:

[res, 0.0]
[print, string]

Now, how can I access the index where the value "res" occurred?

Upvotes: 1

Views: 9606

Answers (2)

ΦXocę 웃 Пepeúpa ツ
ΦXocę 웃 Пepeúpa ツ

Reputation: 48258

Iterate over the list in the list:

List<List<String>> dList = new ArrayList<>();
    dList.add(Arrays.asList("A", "B", "C"));
    dList.add(Arrays.asList("A", "B", "C"));
    dList.add(Arrays.asList("A", "B", "C"));
    for (List<String> list : dList) {
        if (list.contains("A")) {
        // todo
        }
    }

or use a java8 stream

example:

List<List<String>> dList = new ArrayList<>();
    dList.add(Arrays.asList("A", "B", "C"));
    dList.add(Arrays.asList("f", "t", "j"));
    dList.add(Arrays.asList("g", "4", "h"));

    String a = dList.stream().flatMap(List::stream).filter(xx -> xx.equals("a")).findAny().orElse(null);
    a = dList.stream().flatMap(List::stream).filter(xx -> xx.equalsIgnoreCase("a")).findFirst().orElse(null);
    a = dList.stream().flatMap(List::stream).filter(xx -> xx.equals("h")).findFirst().orElse(null);

Upvotes: 2

Kevin Anderson
Kevin Anderson

Reputation: 4592

If list is your list, you should be able to find the value "res" with:

list.get(0).get(0)

For a reference a[row][col] to an element of a 2d array, the equivalent reference to an ArrayList of ArrayLists (or really any List of Lists) will be list.get(row).get(col)

Upvotes: 4

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