Top 8 Core Java Concepts That You Must Know

Whether you are a novice or an experienced Java programmer, you should be familiar with numerous fundamental Java ideas. Learning to program in a language such as Java can be difficult. Unlike other programming languages, Java offers a plethora of ins and outs that can be intimidating.

How can you keep yourself motivated to learn? Maintaining a cheerful attitude is critical. Moreover, when you have good fundamental programming skills, expanding your knowledge to other languages and technologies becomes easy.

Understanding the inner workings of Java programming and its fundamentals provide numerous benefits. For instance, it will simplify your life if you are programming in Java. Additionally, it will help you spend less time troubleshooting your programming. In many instances, you can utilize your knowledge to your advantage during an interview.

You can learn more about Java fundamentals by taking a Java tutorial.

This article will assist you in reinforcing your knowledge of Java programming core concepts. It serves as a quick reference guide to tools and information on critical Java principles.

Top Core Java Concepts

This article discusses several high-level Java basic ideas and then delves deeper into specific subtopics. 

  • Interfaces

In Java, you will write code against an interface rather than an implementation.

This is sometimes referred to as programming to interfaces, and it refers to a technique for writing classes that are based on an interface that describes the behavior of the object. This design approach may appear to be more work at first because it requires the following three steps:

  • Construct an interface.
  • Define its procedures.
  • Create a class that contains the implementation.

This Java approach, on the other hand, assures that you are:

  • Using variables with an interface type.
  • Return method types or method argument types.

What’s amazing about these stages is that they make Java code more adaptable and testable.

  • Java execution

In Java, two fundamental execution units are the process and the thread. In Java, the terms process and thread are defined as follows:

The term “process” refers to a self-contained execution environment that can be a program or an application. When seen as a program, it is composed of several processes. A Java runtime environment is a single process that executes. Additionally, the process itself is composed of several classes and programs.

Thread: Exists within the process. It is created using fewer resources and shares process resources. Similarly, a thread is a lightweight process.

Using threads in Java has several significant advantages:

  • Threads are created more quickly and with fewer resources since they are lightweight operations.
  • Threads share the data and code of their parent process.
  • Generally, context switching between threads is less expensive than moving between processes.
  • Thread-to-thread communication is comparatively straightforward in comparison to process-to-process communication.
  • Java also supports multithreading, depending on the application.
  • Programming in an Object-Oriented Manner (OOP)

OOP, which stands for object-oriented programming, is a critical concept in Java. Java places a higher premium on data than on functions. OOP programming languages are based on the concept of objects.

This object encapsulates both data and the methods that operate on it. This safeguards data by enclosing the methods within the object. Objects communicate with one another via messages in OOP. The following functionalities are supported by all OOP languages (including Java):

  • Classes.
  • Encapsulation.
  • Abstraction.
  • Inheritance.
  • Polymorphism.

Polymorphism is a critical characteristic of OOP. Polymorphism enables Java to provide many forms for objects or entities. In Java, for example, a method with various implementations is polymorphic. Polymorphism in Java is classified into two types:

  • Polymorphism with Overloading: The polymorphic/overloaded method is resolved at compile time. Additionally, Overloading Polymorphism is referred to as Compile Time Polymorphism.
  • Overriding Polymorphism: In runtime polymorphism, a Java program’s call to an overridden method resolves at runtime. Additionally, Overriding Polymorphism is referred to as Runtime Polymorphism.
  • Non-Primitive Data Types

Because they refer to objects, non-primitive data types are reference types. The following are the primary distinctions between primitive and non-primitive data types:

  • Java predefines primitive types, but not non-primitive types (except for String). Non-primitive types are created by the programmer.
  • Non-primitive types can be used to invoke methods that execute specific operations, whereas primitive types cannot.
  • A primitive type is always assigned a value, whereas non-primitive types are allowed to be null.
  • A primitive type begins with a lowercase letter, whereas an uppercase letter begins a non-primitive type.
  • A primitive type’s size is dependent on the data type, whereas non-primitive types all have the same size.
  • Classes and Objects

Simply put:

  • A class is a design prototype or as a blueprint.
  • These blueprints aid in the creation of objects.
  • Objects are helpful in refering to instances of classes.

In more depth, every object-oriented programming language supports classes. Additionally, they can be used to group related data.

The behavior of objects is represented through data Variables (sometimes called member variables) and methods. These are referred to as class instances.

In other words, an object encapsulates the state of an entity represented by a class at any point in time. Typically, an object consists of the following:

  • The traits or characteristics of an object at a certain point in time.
  • Methods represent an object’s activity and define how objects communicate.
  • Gives the object a unique name.
  • Packages

You can create packages by grouping classes and interfaces that share a common functionality or dependency. Packages enable you to collect and organize your Java code more easily.

  • Fields

A field is a type of variable that is associated with a class or object.

For example, the Car Class may define a field named brand. While all Car objects will contain this brand property, its value will vary for each instance of the class.

This enables Car objects to be distinct from one another while still retaining the fundamental characteristics of all cars.

  • Constructors 

A constructor is a particular method in Java that allows you to initialize objects. Java invokes the constructor when a class object is created. Additionally, constructors can be used to initialize object characteristics.

Constructors are used to assign values to fields that are unique to that instance of the object. For instance, if you’re constructing a Car object, you may need to inform the program about the car’s brand, color, speed, and direction of travel. When an object is formed during program execution, a constructor enables you to simply perform these operations.


If you’re new to Java, this brief overview of the most fundamental core principles in Java (and OOP in general) might serve as an excellent cheat sheet on your way to more efficient and productive writing. If you’re an experienced senior developer, this collection of the top Java concepts will serve as an excellent reminder of what’s critical to know.

The average salary of a Java developer is Rs 4.5 lakhs and it is set to grow up to Rs 5.2 lakhs in the coming years.

Once you have a firm grasp on these fundamental concepts, you can begin writing your own Java programs.

When you are unfamiliar with many of these concepts, they may appear slightly abstract. Once you begin coding in Java, all of the components will fall into place. Java programming has numerous advantages and these core concepts will help you succeed as a Java programmer.

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