How to print combinations of Strings from String arrays in an ArrayList (Java)

Question

So I have an ArrayList<String[]> list which contains some String[] that I need to get the combinations of.

So if list contained A = {a,b,c} and B = {d,e,f} I want to print

ad,ae,af,bd,be,bf,cd,ce,cf

I am just having trouble seeing how I would have one fixed array then get the other so I can iterate through that.

Edit: To clarify I am trying to do this for N String[] so I cant just get the 0th and 1st element.

Answer 1

Iterate over two arrays and on each step make new string combination. After all just print combinations in some way.

    List<String[]> input = ...;
    Set<String> allCombinations = new HashSet<>();
    for (int i = 0; i < input.size() - 1; i++) {
        for (int j = i + 1; j < input.size(); j++) {
            allCombinations.addAll(twoArraysCombinations(input.get(i), input.get(j)));
        }
    }
    // print allCombinations


private static Set<String> twoArraysCombinations(String[] first, String[] second) {
    Set<String> result = new HashSet<>();
    for (String f : first) {
        for (String s : second) {
            result.add(f + s);
        }
    }
    return result;
}

Answer 2

Edit: Author changed his question to specify that there are more than 2 lists in an array. This answer works for 2, but it can used to expand to more. It's still unclear if we wants ALL possible combinations, or just combinations of 2

Use nested loops to iterate over both ArrayLists and then concatenate and print the strings.

If both String[] arrays are in the ArrayList you should pull them out first with String[] A = yourArrayList.get(0) and String[] B = yourArrayList.get(1)

for (String aString : A) 
    for (String bString : B)
        System.out.println(aString + bString);

Answer 3

You can use:

for (String a: list.get(0)) {
   for (String b: list.get(1)) {
      System.out.println(a + b);
   }
}

Where list is your original List<String[]>

Answer 4

Just use 2 for-loops

  String a [] ={"a","b","c"};
  String b [] ={"a","b","c"};
  ArrayList<String> d = new ArrayList<>();
  for (String a1 : a) {
    for (String b1 : b) {
    d.add(a1 + b1);
                        }
                      }
  System.out.println(d.toString());

Answer 5

Impressed with the answers so far....Read the question first guys

I'll give you an outline of a solution (warning typos?). I'll leave it up to you to decide how to put commas between entries and other little intricacies incase this is a homework question. Another poster showed how to put the items in a list instead of printing them. Depending on your exact needs, you may want to merge my example with theirs.

List<String[]> stringLists = ....

for(int firstListIndex = 0; firstListIndex < stringLists.size(); firstListIndex++){
    String[] primaryList = stringLists.get(firstListIndex);
    for(int secondList = firstListIndex + 1; ....){
             String[] secondaryList = ....
             for(String first : primaryList){
                 for(String second : secondaryList){
                     System.out.println(first + second);
                 }
             }

    }

}