Convert String to ArrayList<String> in Java

Question

I have a String line "PAA...P.....P..XX.B..Q.OBCCQ.ORRRQ.O" which has 36 characters and I want to distribute them by 6 elements into ArrayList, but I'm not sure how I can do that.

I want inside of ArrayList to look like,

[["PAA..."],["P....."],["P..XX."],["B..QO"],["BCCQ.O"],["RRRQ.O"]]

and each index has a split string by 6.

Thanks!

Answer 1

You can do it like so:

String s = "PAA...P.....P..XX.B..Q.OBCCQ.ORRRQ.O";
List<List<String>> result = Arrays.stream(s.split("(?<=\\G.{6})"))
    .map(Arrays::asList).collect(Collectors.toList());
System.out.println(result);

Output:

[[PAA...], [P.....], [P..XX.], [B..Q.O], [BCCQ.O], [RRRQ.O]]

Explanation of the regex at regex101 :

Answer 2

If you just want a list of list of strings that are of length groupSize . This will work with any groupSize. The last string will be the remainder if the length is not a multiple of groupSize.

I took the time to provide two options since your description didn't seem to match the desired output.

The first, list1, is a list of lists where each list contains a single 6 character string. List2 is a single list of 6 character strings.

List<List<String>> list1 = new ArrayList<>();
List<String> list2 = new ArrayList<>();
int len = str.length();
int groupSize = 6;
for (int i = 0; i < len; i += groupSize) {
    // option 1
    list1.add(new ArrayList<>(List.of(str.substring(i, (len - i) > groupSize ?
                    i + groupSize : len))));
    // option 2
    list2.add(str.substring(i, (len - i) > groupSize ?
            i + groupSize : len));
}

System.out.println("list1 = " + list1);
System.out.println("list2 = " + list2);

Prints

list1 = [[PAA...], [P.....], [P..XX.], [B..Q.O], [BCCQ.O], [RRRQ.O]]
list2 = [PAA..., P....., P..XX., B..Q.O, BCCQ.O, RRRQ.O]

Answer 3

String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
        ArrayList outer = new ArrayList(); // answer
        ArrayList inner = new ArrayList();
        int groupOf = 6;
        for (int i=0; i< str.length(); i ++){
            inner.add(str.substring(i,i+1));
            if (inner.size() == groupOf){
                outer.add(inner);
                System.out.println(outer);
                inner.clear();
            }
        }