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?
2 Answers
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)
2 Comments
dumbPotato21
see the comments. This is not what the OP wants
BoJack Horseman
No. I have to get the index where res occurred. Its like list.get().get().indexOf("res"). Instance of res could be any value. For example, indexOf(print), etc.
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);
answered May 14, 2017 at 9:07
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2 Comments
BoJack Horseman
I think this is what I'm looking for but is there any way, that I can do this without looping? I need to be time efficient in this problem. Anyway, thank you.
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time efficiency is going to be hard, find in a list is a Olog(n), now imagine finding in a list of list, maybe modifying that design can help improving the efficiency....
list.get(0).get(0).