java for each loop expects object as type while it contains an integer array

Question

I got a beginner's Java question.

I am filling an ArrayList like this:

   private ArrayList getDuplicatesIndexes(char[] letters) {
        ArrayList<int[]> duplicatesIndexes = new ArrayList<int[]>();

        for(int i = 0; i < letters.length; i++ ) {

            for(int j = 0; j < letters.length; j++) {
                System.out.println("compare this");
                System.out.println(letters[i]);
                System.out.println("with this:");
                System.out.println(letters[j]);
                if(letters[i] == letters[j] && i != j) {
                    System.out.println("match!");
                    int[] indexes = new int[2];
                    indexes[0] = i;
                    indexes[1] = j;
                    duplicatesIndexes.add(indexes);
                }
            }
        }

        return duplicatesIndexes;
    }

I want to loop through it like this:

private void checkForSingularLetters(ArrayList duplicatesIndexes, char[] letters) {
        for(int[] indexes : duplicatesIndexes ){
            System.out.println(indexes[0]);
            ...
        }


}

I cant wrap my mind about why the foreach loop is expecting an object while im sure its filled with int[]

Maybe someone could explain it to me. Thanks.

Answer 1

You are using the raw form of ArrayList in your method checkForSingularLetters, so that means that Object is expected when iterating. After all, a raw ArrayList could contain anything.

Use the generic form of ArrayList in your method parameter:

private void checkForSingularLetters(ArrayList<int[]> duplicatesIndexes, char[] letters) 

Answer 2

You have an untyped ArrayList which contains Object by default - try extending the method signature by ArrayList<int[]> duplicatesIndexes,