Viruses can be spread by ________ apps, and it is a good idea to have an antivirus program installed on your smartphone

Briefly describe the similarities and differences between abstract classes and interfaces.

What will be an ideal response?

What is the output of the following code?

``` public class Test { public static void main(String[] args) { String s1 = new String("Welcome to Java!"); String s2 = new String("Welcome to Java!"); if (s1 == s2) System.out.println("s1 and s2 reference to the same String object"); else System.out.println("s1 and s2 reference to different String objects"); } }``` a. s1 and s2 reference to the same String object b. s1 and s2 reference to different String objects