public class CustomString {      String myString;      boolean isSet;      public CustomString() {         this.myString = null;         this.isSet = false;     }      /**      * Returns a new string version of the current string where the alphabetical characters specified in the given arg, are removed.      *         * The alphabetical characters to be removed are case insensitive.        * All non-alphabetical characters are unaffected.      * If the current string is null, empty, or has not been set to a value, this method should return an empty string.      *      * Example(s):      * - For a current string "my lucky numbers are 6, 8, and 19.", calling remove("ra6") would return "my lucky numbes e 6, 8, nd 19."      * - For a current string "my lucky numbers are 6, 8, and 19.", calling remove("6,.") would return "my lucky numbers are 6, 8, and 19."      * - For a current string "my lucky numbers are 6, 8, and 19.", calling remove("") would return "my lucky numbers are 6, 8, and 19."      *       * Remember: This method builds and returns a new string, and does not directly modify the myString field.      *       * @param arg the string containing the alphabetical characters to be removed from the current string      * @return new string in which the alphabetical characters specified in the arg are removed      */

Please help me with this task. Thank you!

public class CustomString {

     String myString;

     boolean isSet;

     public CustomString() {
        this.myString = null;
        this.isSet = false;
    }

     /**
     * Returns a new string version of the current string where the alphabetical characters specified in the given arg, are removed.
     *   
     * The alphabetical characters to be removed are case insensitive.  
     * All non-alphabetical characters are unaffected.
     * If the current string is null, empty, or has not been set to a value, this method should return an empty string.
     *
     * Example(s):
     * - For a current string "my lucky numbers are 6, 8, and 19.", calling remove("ra6") would return "my lucky numbes e 6, 8, nd 19."
     * - For a current string "my lucky numbers are 6, 8, and 19.", calling remove("6,.") would return "my lucky numbers are 6, 8, and 19."
     * - For a current string "my lucky numbers are 6, 8, and 19.", calling remove("") would return "my lucky numbers are 6, 8, and 19."
     * 
     * Remember: This method builds and returns a new string, and does not directly modify the myString field.
     * 
     * @param arg the string containing the alphabetical characters to be removed from the current string
     * @return new string in which the alphabetical characters specified in the arg are removed
     */
    public String remove(String arg) {

        //I don't understand

    }

}