Integer cannot be applied error to java.lang.string

Integer.toString() converts an Integer Object to String.

timesTable + " X " + i + " = " + i * timesTable returns a String value by itself. So you can directly add this to your code as follows:

ArrayList<String> timesTableContent = new ArrayList<>();

for (int i = 1; i <= 10; i++) {

    timesTableContent.add(timesTable + "      X     " + i + "      =     " + i * timesTable);

In your code, you are passing a String Object in a method that actually accepts an Integer value. That's the whole problem.

EDIT: You are calling Integer.toString() on a String, when the method only accepts an Integer. This is why you get the error message you provided.

I believe you have misplaced your parenthesis a little bit.

You could build the string you want with:

ArrayList<String> timesTableContent = new ArrayList<>();

int timesTable = 2;

for (int i = 1; i <= 10; i++) {
    timesTableContent.add(timesTable + 
                          "      X     " + 
                                       i + 
                          "      =     " + 
                          (i * timesTable));
}

Why do you use Integer.toString call? Try removing it.

Instead of Integer.toString() try to concatenate integer using String.valueOf()

Instead of

ArrayList<String> timesTableContent = new ArrayList<>();

for (int i = 1; i <= 10; i++) {

    timesTableContent.add(Integer.toString(timesTable + "      X     " + i + "      =     " + i * timesTable));

Replace this

ArrayList<String> timesTableContent = new ArrayList<>();

for (int i = 1; i <= 10; i++) {
    timesTableContent.add(timesTable + "      X     " + String.valueOf(i) + "      =     " + String.valueOf(i * timesTable)));
}

But instead of use this

Just concatenate without convert it. Thanks