One of the more obvious errors occurs when a public Java class is named differently than the file that contains the class definition. This is demonstrated in the next screen snapshot.

However, unlike public access, the code must be located in a class that belongs to the same package (discussed later in the Java 101 series) as the class containing the member that is to be accessed.

there's a basic and often violated software design principle pertaining to Java method modifiers that is in need of explanation. A public method should never be called by another public method within ...