Please answer questions 3.19 in java:

Chapter 3. Primitive Types and s String pThis String q Stringr not a string." System out println((pength ogramming Practice the following program and observe the error reported by the compiler 1 public class UninitializedString t public static void main (String args String greeting System.out.printin (greeting 6 Now initialize the greeting object and rerun the program. Why does the program compile now? Write a Java program that prompts the user to enter the number of rooms in her home, uses a Scanner object to read the input into an int variable named rooms, and then outputs the value on the screen. I you compile and execute your program and type in the value 3.5, can you explain the output y Convert the college cost calculator solution given in Section 3.5 to use JOptionPane methods for both input and output. Use the header giving the user's first and last name for the title of the output dialog and omit the line of asterisks. If you put all the output in a single String with a newline (ln) separating each line, the output will display properly 3.1 9 3.20