Provide a class for authoring a simple letter. In the constructor, supply the names of the sender and the recipient:

Construct an object of the Letter class and call addLine twice.
(1) Use the concat method to form a longer string from two shorter strings.

(2) The special string "" represents a new line. For example, the statement body = body.concat("Sincerely,").concat("");
adds a line containing the string "Sincerely," to the body.

public Letter (String from, String to) Supply a method public void addLine(String line) to add a line of text to the body of the letter. Supply a method public String getText() that returns the entire text of the letter. The text has the form: Dear recipient name: blank line first line of the body second line of the body last line of the body blank line Sincerely, blank line sender name