About JAVA Language :-

1. Java is a high-level programming language originally developed by Sun Microsystems and released in

1995. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.

  

2. open-source, free,

3. Java is an object-oriented, class-based, concurrent, secured, simple, Multithreaded, Distributed and general-purpose computer-programming language. It is a widely used robust technology. It has a huge community support (tens of millions of developers)

4. It is owned by Oracle, and more than 3 billion devices run Java. 

It is used for:

Portable,  Mobile applications (specially Android apps), Desktop applications, Web applications,  Web servers and application servers, Games Development, Database connection, And much, much more |

Java Syntax:

We created a Java file called Simple.java, and we used the following code to print "Hello World" to the screen:

package simple; //This is user define Package  import java.util.*; //This is Pre define Package  import java.lang.*; //This is Pre define Package public class Simple  { public static void main(String[] args)  { System.out.println("Hello World");  }

} Every line of code that runs in Java must be inside a class. A class should always start with an uppercase first letter. The name of the java file must match the class name. When saving the file, save it using the class name and add ".java" to the end of the filename.

JDK, JRE, and JVM are core concepts of Java programming language.

JDK: - Java Development Kit is the core component of Java Environment and provides all the tools, executable and binaries required to compile, debug and execute a Java Program. JDK is a platform- specific software and that’s why we have separate installers for Windows, Mac, and Unix systems. We can say that JDK is the superset of JRE since it contains JRE with Java compiler, debugger, and core classes. The current version of JDK is 11 also known as Java 11.

JVM: - Java Virtual Machine is the heart of Java programming language. When we run a program, JVM is responsible for converting Byte code to the machine specific code. JVM is also platform dependent and provides core java functions like memory management, garbage collection, security etc. JVM is customizable and we can use java options to customize it, for example allocating minimum and maximum memory to JVM. JVM is called virtual because it provides an interface that does not depend on the underlying operating system and machine hardware. This independence from hardware and the operating system is what makes java program write-once-run-anywhere.

JRE: - JRE (Java Runtime Environment) is the implementation of JVM, it provides a platform to execute java programs. JRE consists of JVM and java binaries and other classes to execute any program successfully. JRE doesn’t contain any development tools like java compiler, debugger etc. If you want to execute any java program, you should have JRE installed but we don’t need JDK for running any java program.

Just-in-time Compiler (JIT): - JIT is part of JVM that optimizes byte code to machine specific language compilation by compiling similar byte codes at the same time, hence reducing overall time taken for the compilation of byte code to machine specific language.

JDK vs JRE vs JVM

Let’s look at some of the important difference between JDK, JRE, and JVM.

 JDK is for development purpose whereas JRE is for running the java programs.
 JDK and JRE both contains JVM so that we can run our java program.
 JVM is the heart of java programming language and provides platform independence.

Notes:-
Heap Memory: Heap is a part of JVM memory where objects are allocated. JVM creates a Class object for

each .class file.

Stack Memory: Stack is an also a part of JVM memory but unlike Heap, it is used for storing temporary variables.