The 2021 Java Developer Cheat Sheets You Need to Know About


If you’re just starting your career as a software developer, you probably already know that Java is still one of the most widely used programming languages and is worth your learning efforts in 2021. Initially developed in 1995 and later acquired by Oracle, Java is a high-level open-source programming language that is designed to code Android mobile applications, server networks or whole IoT infrastructures. Java uses pragmatic Object-Oriented Programming (OOP), making objects reusable, which saves developers lots of time and helps them solve complex problems easier.  

From my experience working in a bespoke software development company with devoted Java specialists, I know that mastery-oriented developers always strive to expand their existing knowledge. Whether you are a Senior Java Developer or just entering the vast and exciting field of Java programming, a good helper that comes in handy during stressful situations is a Java Cheat Sheet. The high-quality ones are usually full of summarised practical steps & visually appealing info with the most essential Java features. Now, let’s dive deeper into the most comprehensive Java Cheat Sheets to use in 2021:

Start with the Java Fundamentals

Everyone starts with the basics, but as you acquire more knowledge, it’s easier to forget some of the fundamentals, especially if you haven’t written a Java app from scratch for a while. This all-in-one Cheatography Cheat Sheet is your to-go place in case you need to refresh your memory on how basic Java features behave. Also, it is a good starting point if you just start to get familiar with Java in 2021. 

The cheat sheet shortly mentions Java data types, including integer(int)types for whole numbers like byte, short, long, floating point types for decimal numbers float and double, boolean data types for declaring true or false values & char and String respectively for storing a single character surrounded by single quotes or text sequences in double quotes. It also covers other fundaments like Java Statements, Java Data Conversions, String Methods, Array and Hashmap Lists and many other basics.

Java OOP Cheat Sheet

As I noted, Java is a programming language that embraces Object-Oriented Programming (OOP) and to become a successful Java software developer, you need to learn and fully understand the logic behind the broader concept. Essentially, we have four basic principles that constitute OOP. The first one is inheritance, which is a mechanism designed to make child classes acquire properties from parent classes. The second concept is encapsulation, and it wraps Java fields (states) and Java methods (behaviours) to unite them in a single unit that hides and protects sensitive data from other users. 

The third principle is called polymorphism(dynamic or static), and it lets developers perform single actions in multiple ways, e.g. through method overloading, method overriding, etc. The fourth core idea of OOP is the abstraction that helps distill and show only the essential information to the user, hiding unnecessary details. Here you can take a closer look at the Java OOP cheat sheet

Software Project Management Tools 

Apart from knowing Java syntax and features, you also need reliable project management tools as a software developer. Some of the top-ranking Java dev tools for 2021 include Site24x7, Java Performance Monitoring, JUnit, Apache Maven, Spark etc. Depending on your preference or company’s choice, you’ll have to focus on learning how to code, test and deploy a Java application. 

This concise and well-rounded cheat sheet is a must-have for Java developers. Although it begins with Java 8 Streams for bulk operations, initially introduced more than five years ago, this topic could still be relevant for beginners. Furthermore, the list includes some of the most notable Java libraries & repositories, as well as sneak peeks of Maven’s basic options and plugins, SQL’s basic queries and functions, and also a Regex cheat sheet with the most popular Java classes and methods. 

Java Streams Cheat Sheet 

As I mentioned, Java Streams have been around since Java 8, but they cover so many broad functionalities that it is worth having a separate cheat sheet dedicated to Streams. Keep in mind that a Java stream is not a data structure and will not modify your underlying data source as it doesn’t store any data. Similar to its name, a Stream helps you streamline processes by pipelining functions, storing and transforming data to make it usable for another operation.

The two types of possible operation (method) clashortlysses are intermediate or terminate. Intermediate operations are basically put on hold until a terminal operation, meaning one that the pipeline is consumed and no longer usable, is executed. The Java Stream guide linked above allows you to get an overview of the main Stream operations and their most common purposes. You will learn how and when to use both intermediate operations like filter(), map(), peek() and terminal ones - forEach(), reduce() or collect(). 

Java Collections Cheat Sheets

Java Collections types are designed to group objects together to organise code structure and boost code readability and performance. The Java Collection Framework provides four main interface types: List, Map, Set, and Queue, each of them used to manipulate object groups. Collections also have many classes such as ArrayList, LinkedList, Vector, PriorityQueue and others.

In case you’re interested, you can find separate cheat sheets, for example, HashMap or ArrayList. HashMap in Java represents a container storing key-value pairs and is unsynchronised, unlike HashTable. Each of these keys is unique and assigned only to one value. Generally, the purpose of Java Collections is to sort, search for, insert, delete, iterate objects and make the development process more manageable. 

Biography Aleksandrina Vasileva 

Aleksandrina is a Content Creator at Dreamix, a custom software development company, and is keen on innovative technological solutions with a positive impact on our world. Her teaching background, mixed with interest in psychology, drives her to share knowledge. She is an avid reader and enthusiastic blogger, always looking for the next inspiration.