In object-oriented programming design, such as in Java, your program often consists of two or more classes (often written in different .java source files). One class contains the main() method to generate the console output, while the other classes may just contain properties or methods to process the data. Using this approach to design a DNA sequence class called DNA with a validation method called IsDNAvalid() to validate if the DNA sequence contains any invalid letter (not A, C, G, T). You can use the charAt() method of the String class to loop through a sequence string to check if each letter is valid. Design another class which contains the main()method, and create a DNA object inside the main method, then call the IsDNAvalid() method to validate the DNA sequence input.