Maximizing code reuse in your Java programs means writing code that is easy to read ... you must know how to break it down so that each class and method does one thing well.

Without certainty, it is challenging to write programs that work correctly at runtime. Java assertions provide ... although they are still present in the class file. You can enforce preconditions ...

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: ...