Introduction to Java + Installing Java JDK and IntelliJ IDEA for Java

java exercise and need the explanation and answer to help me learn.

Java was created by Sun Microsystems in the US back in 1981.
James Gosling was the lead developer of Java.
Java has had three major releases.
Microsystems developed Java.
Java was developed in 1981.
The goal of developing Java was to create a simple, reliable language based on C++ but without troublesome features.
The development of Java was focused on creating a good experience for developers.
Java was the first application language of the World Wide Web.
What is Java?
Java is a programming language and a platform. Java is a high level, robust, object-oriented and secure programming language.
Java was developed by Sun Microsystems (which is now the subsidiary of Oracle) in the year 1995. James Gosling is known as the father of Java. Before Java, its name was Oak. Since Oak was already a registered company, so James Gosling and his team changed the name from Oak to Java.
Platform: Any hardware or software environment in which a program runs, is known as a platform. Since Java has a runtime environment (JRE) and API, it is called a platform.\
According to Sun, 3 billion devices run Java. There are many devices where Java is currently used. Some of them are as follows:
Desktop Applications such as acrobat reader, media player, antivirus, etc.
Web Applications such as,, etc.
Enterprise Applications such as banking applications.
Embedded System
Smart Card
Games, etc.
History of Java
The history of Java is very interesting. Java was originally designed for interactive television, but it was too advanced technology for the digital cable television industry at the time. The history of Java starts with the Green Team. Java team members (also known as Green Team), initiated this project to develop a language for digital devices such as set-top boxes, televisions, etc. However, it was best suited for internet programming. Later, Java technology was incorporated by Netscape.
The principles for creating Java programming were “Simple, Robust, Portable, Platform-independent, Secured, High Performance, Multithreaded, Architecture Neutral, Object-Oriented, Interpreted, and Dynamic”.  was developed by James Gosling, who is known as the father of Java, in 1995. James Gosling and his team members started the project in the early ’90s.
Currently, Java is used in internet programming, mobile devices, games, e-business solutions, etc. Following are given significant points that describe the history of Java.
1) , Mike Sheridan, and Patrick Naughton initiated the Java language project in June 1991. The small team of sun engineers called Green Team.
2) Initially it was designed for small,  in electronic appliances like set-top boxes.
3) Firstly, it was called “Greentalk” by James Gosling, and the file extension was .gt.
4) After that, it was called Oak and was developed as a part of the Green project.
Why Java was named as “Oak”?
5) Why Oak? Oak is a symbol of strength and chosen as a national tree of many countries like the U.S.A., France, Germany, Romania, etc.
6) In 1995, Oak was renamed as “Java” because it was already a trademark by Oak Technologies.
Why Java Programming named “Java”?
7) Why had they chose the name Java for Java language? The team gathered to choose a new name. The suggested words were “dynamic”, “revolutionary”, “Silk”, “jolt”, “DNA”, etc. They wanted something that reflected the essence of the technology: revolutionary, dynamic, lively, cool, unique, and easy to spell, and fun to say.
According to James Gosling, “Java was one of the top choices along with Silk”. Since Java was so unique, most of the team members preferred Java than other names.
8) Java is an island in Indonesia where the first coffee was produced (called Java coffee). It is a kind of espresso bean. Java name was chosen by James Gosling while having a cup of coffee nearby his office.
9) Notice that Java is just a name, not an acronym.
10) Initially developed by James Gosling at  (which is now a subsidiary of Oracle Corporation) and released in 1995.
11) In 1995, Time magazine called Java one of the Ten Best Products of 1995.
12) JDK 1.0 was released on January 23, 1996. After the first release of Java, there have been many additional features added to the language. Now Java is being used in Windows applications, Web applications, enterprise applications, mobile applications, cards, etc.
Features of Java
The primary objective of  language creation was to make it portable, simple and secure programming language. Apart from this, there are also some excellent features which play an important role in the popularity of this language. The features of Java are also known as Java buzzwords.
A list of the most important features of the Java language is given below.
Java is very easy to learn, and its syntax is simple, clean and easy to understand. According to Sun Microsystem, Java language is a simple programming language because:
Java syntax is based on C++ (so easier for programmers to learn it after C++).
Java has removed many complicated and rarely-used features, for example, explicit pointers, operator overloading, etc.
There is no need to remove unreferenced objects because there is an Automatic Garbage Collection in Java.
Java is an  programming language. Everything in Java is an object. Object-oriented means we organize our software as a combination of different types of objects that incorporate both data and behavior.
Object-oriented programming (OOPs) is a methodology that simplifies software development and maintenance by providing some rules.
Basic concepts of OOPs are:
Platform Independent
Java is platform independent because it is different from other languages like , , etc. which are compiled into platform specific machines while Java is a write once, run anywhere language. A platform is the hardware or software environment in which a program runs.
Java is best known for its security. With Java, we can develop virus-free systems. Java is secured because:
No explicit pointer
Java Programs run inside a virtual machine sandbox
ADClassloader: Classloader in Java is a part of the Java Runtime Environment (JRE) which is used to load Java classes into the Java Virtual Machine dynamically. It adds security by separating the package for the classes of the local file system from those that are imported from network sources.
Bytecode Verifier: It checks the code fragments for illegal code that can violate access rights to objects.
Security Manager: It determines what resources a class can access such as reading and writing to the local disk.
The English mining of Robust is strong. Java is robust because:
It uses strong memory management.
There is a lack of pointers that avoids security problems.
Java provides automatic garbage collection which runs on the Java Virtual Machine to get rid of objects which are not being used by a Java application anymore.
There are exception handling and the type checking mechanism in Java. All these points make Java robust.
Java is architecture neutral because there are no implementation dependent features, for example, the size of primitive types is fixed.
In C programming, int data type occupies 2 bytes of memory for 32-bit architecture and 4 bytes of memory for 64-bit architecture.
Java is portable because it facilitates you to carry the Java bytecode to any platform. It doesn’t require any implementation.
Java is faster than other traditional interpreted programming languages because Java bytecode is “close” to native code. It is still a little bit slower than a compiled language (e.g., C++). Java is an interpreted language that is why it is slower than compiled languages, e.g., C, C++, etc.
Java is distributed because it facilitates users to create distributed applications in Java. RMI and EJB are used for creating distributed applications. This feature of Java makes us able to access files by calling the methods from any machine on the internet.
A thread is like a separate program, executing concurrently. We can write Java programs that deal with many tasks at once by defining multiple threads. The main advantage of multi-threading is that it doesn’t occupy memory for each thread. It shares a common memory area. Threads are important for multi-media, Web applications, etc.
Java is a dynamic language. It supports the dynamic loading of classes. It means classes are loaded on demand. It also supports functions from its native languages, i.e., C and C++.
Java supports dynamic compilation and automatic memory management (garbage collection).
class Simple{  
    public static void main(String args[ ]){  
     System.out.println(“Hello Java”);  

Compilation Flow:
When we compile Java program using javac tool, the Java compiler converts the source code into byte code.
Parameters used in First Java Program
class keyword is used to declare a class in Java.
public keyword is an access modifier that represents visibility. It means it is visible to all.
static is a keyword. If we declare any method as static, it is known as the static method. The core advantage of the static method is that there is no need to create an object to invoke the static method. The main() method is executed by the JVM, so it doesn’t require creating an object to invoke the main() method. So, it saves memory.
void is the return type of the method. It means it doesn’t return any value.
main represents the starting point of the program.
String[] args or String args[] is used for . We will discuss it in coming section.
System.out.println() is used to print statement. Here, System is a class, out is an object of the PrintStream class, println() is a method of the PrintStream class. We will discuss the internal working of System.out.println() statement in the coming section.

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