Working with instances of the immutable String class

The String class, specifically the java.lang.String class, represents character strings and is an immutable class that generates non-mutating objects. Hence, the methods provided by the String class do not mutate the object.

For example, the following lines create a new String, that is, a new instance of the java.lang.String class named welcomeMessage with an initial value of "Welcome to Virtual Creatures Land". Then, the code makes many calls to System.out.println with welcomeMessage followed by a different method as an argument. First, we call the toUpperCase method to generate a new String with all the characters converted to uppercase. Then, we call the toLowerCase method to generate a new String with all the characters converted to lowercase. Then, we call the replaceAll method to generate a new String in which the spaces were replaced by a hyphen (-). Finally, we call the System.out.println method again with welcomeMessage as an argument...