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.

public final class NegExpr implements Expr { } For example, if we want to write the following class and try to compile it, we get the following error: javac DivideExpr.java DivideExpr.java:1: error: ...

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 ...