Archives for June 2021

Built-in Functional Interfaces In Java 8, there are a lot of method signatures that refer to interfaces in java.util.function. Therefore, it is important to understand what these interfaces do and what variations on the basics exist. It makes writing lambda expressions a lot easier. The java.util.function Package Predicate: An expression that returns a boolean Consumer: […]

Generics Generics provide flexible type safety to your code. They move many common errors from run time to compile-time and provide cleaner, easier-to-write code. Generics also reduce the need for casting with collections and are used heavily in the Java Collections API. Simple Cache Class Without Generic The two examples below show very simple caching […]

Java Interfaces In Java, an interface outlines a contract for a class. The contract outlined by an interface mandates the methods that must be implemented in a class. Classes implementing the contract must fulfill the entire contract or be declared abstract. Java interfaces are used to define abstract types. Interfaces: Are similar to abstract classes […]

Modeling Business Problems with Classes Class Inheritance When designing an object-oriented solution, you should attempt to avoid code duplication. One technique to avoid duplication is to create library methods and classes. Libraries function as a central point to contain often reused code. Another technique to avoid code duplication is to use class inheritance. When there […]

Using Access Control The table below illustrates access to a field or method marked with the access modifier in the left column. Modifier (keyword) Same Class Same Package Subclass in Another Package Universe private Yes – – – default Yes Yes – – protected Yes Yes Yes – public Yes Yes Yes Yes The access […]

Encapsulation Encapsulation is one of the four fundamental object-oriented programming concepts. The other three are inheritance, polymorphism, and abstraction. The term encapsulation means to enclose in a capsule or to wrap something around an object to cover it. Encapsulation covers, or wraps, the internal workings of a Java object. – Data variables, or fields, are […]

This post is a review of fundamental Java and programming concepts. Java Class Structure A Java class is described in a text file with a .java extension. In the example shown below, the Java keywords are highlighted in bold. package [package_name]; import [other_packages]; public class ClassName { [variables(also known as fields)]; [constructor(s)]; [other methods]; } […]