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So I have been looking into different ways to optimize and tune my code, when I ran into an article about strings. Now there are two types of objects in java, mutable objects, and immutable object; rather, changeable and unchangeable objects. Unfortunately, a String is among those immutable objects. It cannot change once it has been created. Now you say, "Well, how is that possible? It's easy to set a String to a new value!" Of course that it is easy, but that is because the String class handles all the low level operations to 'modify' the String. For example, let's say we have a simple class that takes a name input import java.io.Serializable; import java.util.Scanner; public class RegisterUser implements Serializable { private static transient Scanner iReader; private static transient boolean nameOK = false; private static String username = null; public static void main (String args[]) { println("Hello, Welcome to the new user registration."); println("Fortunately, all we need at this point is your name."); iReader = new Scanner(System.in); while (!nameOK) { println("If you please, what is your first name?"); username = formatCase(iReader.nextLine()); println("Is " +username+ " correct? if it is, please enter Y"); if (scanner.nextLine().toString().equalsIgnoreCase("y")) nameOK = true; } nameOK = false; while (!nameOK) { println("Thank you. Now, what is your last name?"); String lastName = formatCase(iReader.nextLine()); println("Is " +lastName+ " spelled right? if it is, please enter Y"); if (scanner.nextLine().toString().equalsIgnoreCase("y")) { nameOK = true; username += " " + lastName; } } println("Thank you very much, " +username+ ", your username has successfully been registered."); } static String formatCase(String s) { return (s.length()>0) ? Character.toUpperCase(s.charAt(0))+s.substring(1) : s; } static void println(String s) { System.out.println(s); } } This class, from our point of view, is simple, and gets the job done quick. However, if we were to modify this to serve a large number of users concurrently, we'd run into a problem. When we do things, such as modify a string, we are not actually modifying it. We are creating two objects to replace it. When we used the line:
