Here's a Java program to convert an ArrayList to a String and vice versa:

import java.util.ArrayList;
import java.util.Arrays;

public class ArrayListToString {
    public static void main(String[] args) {
        // Convert ArrayList to String
        ArrayList<String> fruits = new ArrayList<>(Arrays.asList("Apple", "Banana", "Cherry"));
        String fruitsString = String.join(",", fruits);
        System.out.println("ArrayList to String: " + fruitsString);

        // Convert String to ArrayList
        String numbersString = "1,2,3,4,5";
        ArrayList<String> numbers = new ArrayList<>(Arrays.asList(numbersString.split(",")));
        System.out.println("String to ArrayList: " + numbers);
    }
}

In this program, we first create an ArrayList called fruits containing some strings. We then use the String.join method to join the elements of the ArrayList with a separator (a comma in this case) to convert it to a String. The resulting String is then printed to the console.

Next, we define a String called numbersString containing comma-separated numbers. We use the String.split method to split the String into an array of strings, and then create a new ArrayList containing those strings to convert the String to an ArrayList. The resulting ArrayList is then printed to the console.

You can modify the ArrayList and String values to convert different lists to strings and vice versa. Note that if the elements in the ArrayList or String contain commas or the separator character, you will need to use a different separator or a different method for joining or splitting the values.