"In Java, everything is a class or belongs to a class. A class is an extensible program or blueprint for creating objects. Objects are an integral part of OOP that we’ll explore later. However, to start out our programs will be simple enough that they can be contained in a single class. To declare a class, you use the following syntax: public class HelloWorld { ... } where the contents of the class are placed between the opening/closing curly brackets. In addition, a class must be placed in a Java source file with the same name. In our previous example, the class must be in a file named HelloWorld.java. When naming classes, the most commonly accepted naming convention is to use uppercase camel casing (also called PascalCase) in which each word in the name is capitalized including the first, Employee, SavingsAccount, ImageFile, etc. Class names, as well as their source file names, are case sensitive."