Java Basics: A Beginner's Guide to Learning the Fundamentals

 To take your career to next level, the best way to do that is to learn and become an expert in a programming language. This tutorial contains all the tutorials that will take you in simple systematic order starting from the beginner’s level to the advanced topics.

If you’re new to Java and want to know where to start, check out this Core Java Basics Tutorial that will take you through the fundamentals of the programming language and some of its key features.

It also includes resources and other helpful articles that will help you along the way with your core java learning journey.

Core Java - Overview

Java is a popular programming language and one of the most used languages in the world. You can think of it as an imperative and object-oriented language. The word core refers to its core features, which are very similar to those of C++ and C, with some differences.

The core features are classes, objects, strings, arrays, and operators.

This tutorial will teach you all these concepts in detail. The tutorial will take you through simple systematic order starting from beginner’s level to advanced topics. There are many tutorials that will help you master Core Java from scratch.

If you want to learn Core Java quickly, then this blog post on Core Java basics is just for you.

 Object Oriented Concepts

Java is an object-oriented programming language that enables programmers to work with data as objects. In object-oriented programming, you can create new types of objects or extend existing types by adding new fields or methods.

An object is a named collection of data (fields) and behaviors (methods) that interact with each other.

Objects are created in different ways depending on what type they are representing; for instance, if you're creating a Dog object, you could use the phrase new Dog(Spot) to define it; this would create an instance of the Dog class that would be called Spot.

The idea behind objects is to provide a way for us to represent real-world entities in our programs such as people, dogs, and cars. By creating these types of objects we are able to interact with them much as we do in the real world. 

Data Types and Operators

The data types in Core Java are divided into two categories, namely primitive and non-primitive. The primitive types are boolean, char, byte, short, int, and long. The non-primitive types are arrays and strings.

Arrays can be one-dimensional or multi-dimensional whereas strings can only be one-dimensional.

The operators that are used with these data types include addition (+), subtraction (-), multiplication (*), division (/), modulo (%), and assignment (=). Each operator takes two operands.

In order for an operator to work with a type of data it must follow the rules for that particular type of data.  For instance, when adding integers together you would need to use the addition (+) operator because this is what is expected by both integers.

When multiplying integers together you would need to use the multiplication (*) operator because this is what is expected by both integers.

The division between integers would require using the division (/) operator since this is what’s expected by both numbers while when dividing a float value by another float value, we would need to use the divide (/) operator since floats are expecting floating point divisions rather than integer divisions.

Finally, we have modulo which is equivalent to remainder so if we were dividing two whole numbers then we would use the remainder (%) function instead of any other function because there will not be any fractional part of our number left over after performing the operation.

Interface, Abstract Class

The interface provides a name for a group of methods that can be implemented by classes. The interface does not provide any implementation for these methods, nor does it contain any code.

It only contains method declarations and signatures, and any class that implements the interface must provide implementations for all these methods. 

An abstract class can't be instantiated but is used as a blueprint or template from which other classes are derived from.

Abstract classes allow some of their members to be declared as abstract; these are known as abstract methods or abstract fields, which must be implemented in any class that is derived from this class - whether directly or indirectly.

Abstract classes can also contain non-abstract members (known as concrete members). These are simply regular instance variables and fields with no special modifiers applied.

String Manipulation

Strings are an immutable sequence of characters. There are two main ways to create a string in Java: by using a string literal, or by creating a new String object via the new operator. The following examples use both techniques.

String literals can be created with either single or double quotes. Double quotes are needed if you want to include quotation marks within your strings.  String objects should be used when you need to dynamically change strings.

String manipulation is used for processing character data. Some string manipulation functions can convert from one string format to another, search for strings within other strings, extract substrings from larger strings and compare strings. 

One common string manipulation task is to find the index where a substring starts inside of a string. The String class has three methods that return this value: indexOf(), lastIndexOf() and startsWith().

They each take a string parameter and start searching at the beginning of the string on which they are invoked (either passed as an argument or implicitly referenced).

If the substring does not exist in the invoking string, then all three return -1. Otherwise, these functions each return an integer containing its starting position within the invoking string. 

Arrays

An array is a data type that stores a group of values. They are used when you need to store a lot of items in one place, but there is no specific order.

Arrays always have an index number so that they can find the right value if needed. Arrays can be manipulated by adding or removing values.  The array has both an upper and lower limit, which means that once you reach either the upper or lower limit, you can't add any more items.

You'll also notice that arrays start with index 0, meaning they're zero-based. In other words, the first item has index 0 and not 1. This means arrays are easy to understand because we use numbers for them and we know how many items are in each position (index).

One important thing to note about arrays is that you cannot change the size of an array once it has been created.

Annotation and Enum

Annotations are a way for you to store information about your code and how it should be handled by tools. Annotations can be used for things like marking an annotation type or specifying parameters for a method.

One popular use of annotations is in Java annotations for adding metadata that may not otherwise have been available, such as the date and time when a file was last modified or the author of a comment.

Enums provide data types with limited values that can be used as constants. You define enums using the enum keyword followed by one or more names and then a list of possible values.

Collection & Generics

The collection is a type of generic class that can store multiple objects. It provides various methods to manipulate the collection and its elements. The Collection interface extends from the Iterable interface and implements both the List interface and Set interface.

A set does not allow duplicate elements, while a list does not have this restriction. Collections are used in many ways in Core Java Programming, such as storing data sets or lists of items. The usage of collections is dependent on the problem at hand.

One of the key things to remember about collections is that they must be immutable; so if you want to make changes to a collection, you need to create a new one. 

IO Operations

In this tutorial, you will learn how to use IO operations in Core Java. An Input-Output operation is a process that involves information flowing in and out of a system. This can be done by reading or writing data from or to a device or file.

Input/output usually deals with physical devices like disk drives, tapes, printers, etc. One common form of input-output (I/O) is a screen display, which reads information stored on the screen into a computer and prints text and images back onto the screen as output.

The main methods used for input/output are FileReader(), FileWriter(), BufferedReader(), etc.  

Exception Handling

Exceptions are thrown when a particular condition is encountered in the program that can't be handled. The exception handling block of code will handle any potential exceptions and provide you with an alternative course of action. 

Exceptions are classed into two types – unchecked exceptions and checked exceptions.

Checked exceptions are those which will be declared in the method’s signature, whereas unchecked exceptions may occur during execution and hence will not be declared in the method’s signature.

In order to deal with these unchecked exceptions, the try-catch statement comes into play. It allows you to put a piece of code in a try block, followed by one or more catch blocks.

The try block defines what should happen if everything goes well while the catch blocks define what should happen if something goes wrong. 

If there is no matching catch clause then this results in an error being generated.

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