This year we are celebrating 25 years of java, isn't it amazing to learn more about Java? Most people are aware of the java program and each year it’s getting bigger and better. Let me give a small introduction about this popular program, Java is a high level programming language first developed by Sun Microsystems and released in 1995. Java runs on almost all types of operating system platforms such as Windows, Linux, UNIX, and Macintosh. In this Core Java tutorial, you will be learning from basic to advanced level concepts, which will give you in-depth knowledge of the language. We have designed these Core java tutorial concepts to not only teach theoretical concepts but also practical examples. Are you excited to learn this tutorial? Let’s begin,
Java is one of the popular programming languages first developed by James Gosling and other engineers at Sun Microsystems. First, it was developed to use in the distributed environment setup of the internets. Java language developed to run on various platforms such as Windows, Linux, UNIX, and Macintosh. Java is an object-oriented language and works well with other languages too. Now Oracle has taken over the “Java '' Sun microsystems, so all the products of sun microsystem which come under Oracle license. In recent times, Java has become more than a language as time passes. It is also known as a “platform”, this is because it has its own runtime environment, has its own set of application programming interfaces, and distributed programs through RMI. Java is used to create executable contents and that can be distributed through networks. The name “JAVA” refers to the set of software tools to create and implement the executable contents using the Java programming language.
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As I said earlier, java is a product of Sun Microsystems. The history of the java program starts with a green team of Sun Microsystems. The main aim to develop this program is to provide “simple, robust, platform-independent, portable, high performance, secured, object-oriented, and dynamic”. Now Java is used mainly in mobile devices, games, internet games, e-business solutions, and banking sectors. The following are the significant points of java history:
Versions details:
JDK beta -> 1995
JDK version 1.0 -> january 1996
JDK version 1.1 -> february 1997
J2SE version 1.2 -> december 1998
J2SE 1.3 -> may 2000
J2SE 1.4 -> february 2002
J2SE 5.0 -> september 2004
Java SE 6 -> december 2006
Java SE 7 -> july 2011
Java SE 8 LTS -> March 2014 (latest version).
Java offers many advanced features, in the below diagram you will get some idea;
In the future section, we will be explaining each feature in detail.
Java is a basic programming language for students and working professionals to become a successful software engineer when you are working in software companies. Here are some key advantages of the java programming language.
Now we are using Java SE (standard edition) 8.0, which offers java advancements, widespread popularity, and multiple configurations built on various platform types. For example J2EE for enterprise applications and J2ME for mobile applications.
The latest versions of J2 named Java SE, Java ME, and Java EE. Java is popularly called “Write once and run anywhere”.
Some of the important applications are;
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In this section, we are going to explain different environment setups of Java such as JDK, JRE, and JVM.
First, let me discuss JVM:
1. JVM (Java virtual machine):
Java virtual machine is a type of abstract machine. This one is called a virtual machine because you can’t see them physically. The java virtual machine offers a runtime environment where you can execute the java bytecode. With the help of the java virtual machine, you can also run the programs which are written in any other languages (You can take C and C++) and will be compiled to Java byte code.
You will get a Java virtual machine for both hardware and software platforms. Java virtual machine, Java runtime environment, and java development kit are platform dependent because each operating system is configured using multiple different platforms. One important point to be noted here, Java is platform-independent, and three notions of java virtual machine available such as specifications, instances, and implementations.
The main tasks of JVM are as follows;
2. Java runtime environment (JRE):
JRE means Java runtime environment and it is written as a Java RTE. Java runtime environment consists of software tools that are used to develop java applications. This is used to provide the runtime environment and also the implementation of Java virtual machine. This one physically exists. Java virtual machine also consists of a set of libraries and other files that JVM that uses.
The following diagram will explain the JVM activities which are released by other companies.
3. JDK or Java development kit:
JDK means java development kit. The java development kit is a type of software development environment tool kit, used to develop only java applications and java applets. This Java development kit physically exists. The JDK contains JRE and development tools.
JDK is an implementation of the given java platforms which are released by Oracle corporations;
The java development kit consists of a java virtual machine (JVM) and a few other resources such as an interpreter or loader (Only java codes), a compiler or (java c), an archiver or (jar), and a documentation generator (Javadoc) to complete the implementation of java application.
The main purpose of core java is to define specifications, implementations, and Runtime instances. The following diagram explains the JVM internal architecture; this consists of a class loader, execution engine, and memory as shown below:
Let me explain about components in brief:
The class loader is a fundamental component of JVM and acts as a subsystem that is used only for loading the class files. When you run the java program, first it will be loaded by the class loader. You can see three built-in class loaders in core java,
There are various internal class loaders available offered by JAVA. Suppose you want your own set of class loaders, you just need to extend the class loader class. If you have any doubts on Java, then get them clarified from Java Industry experts on our Java Community!
Here class or method area helps to store the per-class structures like runtime constant pools, the code used for methods, and fields or method data.
This is available in the form of a run time data area where you can allocate the objects.
Usually, core java stacks store data formats. This consists of local variables and partial results. The stack plays a vital part in the method invocation and returns. Here each thread consists of a private java virtual machine stack and creates the same thread multiple times.
The program counter register holds the address of the java virtual machine instructions which are being executed.
This component contains the native methods used for application development.
This execution engine consists of the following components:
Java native interface is a type of framework that offers an interface to communicate between any two applications which are written in any programming language like C, assembly programs, and C++. In general, the core java uses the native interface to send information to the console windows and interact with operating system libraries.
First, let me discuss Core java variables,
A variable is nothing but a container that holds the value during the execution of Java programs. The variables are assigned with data types. Variable is used to locate the memory. There are three types of core java variables such as local, instance, and static types.
Variable: A variable is a name given to a reserved area that allocates the memory. In short, you can refer to it as a name of a memory location. This is a combination of “vary + able” where value can be changed.
Types of variables:
Local variables are declared inside the body of the method. One important point, you can use the variable within that method and methods in the class even aware that the variables exist or not.
A local variable cannot be defined by using any “Static” keywords.
Instance variable can be declared inside the class library but it is visible outside the method body. It can’t be declared as a “Static”. The name was given “instance” because the value is instance-specific and not shared among many other instances.
Static variables are declared as static, and this cannot be declared as a local. Here you can create a single copy of the static variable and share them among other instance classes. Memory allocation of static variables happens when the class is loaded in the memory location.
Data types define the different sizes and values that can be stored in the data variables. There are two types of data types available:
Let me explain them one by one,
Primitive data types include Boolean, char, int, long, float, and double whereas non-primitive data types include classes, arrays, and interface.
Core java primitive data types are the fundamental building blocks of data manipulation. These are also considered as most basic data types of java language.
The following diagram explains the core java data types:
The examples for primitive data types are;
Non-primitive data types: These types of variables are mostly used in the writing of program codes. The examples are classes, arrays, and interfaces, etc.
First, we know the definition of Unicode, Unicode is a universal international standard character encoding that represents the words written in the user-defined programming language.
There are many languages used in Unicode;
The problems which you can deal with Unicode system:
To solve these types of problems a new language was developed using Core java, that is the Unicode system.
In the Unicode system, a character holds the 2 bytes, and core java also uses the 2 bytes for characters.
Lowest value: \u0000
Highest value: \ uffff
Core java operators are types of symbols and used to perform multiple operations. For instance, +, -, *, / etc.
There are many types of java operators available such as,
The core java unary operator requires only one or a single command. In general, unary operators are used to performing various operations like,
The java keywords are also called “Reverse words”. The keywords are a particular form of words that acts as a key to a code. These keywords are predefined words, which cannot be used as an object or variable name.
As I said earlier, Java is an object-oriented programming language. So we can assume that this program has the object-oriented feature, so core java supports the following concepts:
Now let’s know the definitions of classes and objects:
Objects: Objects consist of states and behaviors. For example, a dog- this consists of various states like color, breed, name, and behaviors, barking, and eating. One more definition, an object is an instance of a class.
Class: A class can be defined as a blueprint or templates that specify the behavior or state that object possesses the support type.
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We already know the definition, now it’s time to know the sample program;
Public class Dog {
String breed_type;
Int age;
String color_type;
…..
…..
}
The below are the three types of class variables available;
Conclusion:
I hope I have given full justice to this amazing programming tutorial. In this core java tutorial, we have tried to cover almost basic to advanced level concepts. This tutorial is best suited for those who are already known about computer programs and software programming languages. To get in-depth knowledge in this Core java tutorial, best practice of few java related basic programs. Learning only the theoretical part is not enough to get into top MNC; you should get some practical experience or hands-on experience through joining the online course for a better understanding.
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