JAVA BLOG_1

Let's Start an Awesome language Called "Java"!

           In this blogs by blog you can learn Java Easily with Deep Theory and Examples and another Topic related Programs so you can easily understand what the topic Means.......

 

Blog-1:::DEFINATIONS OF JAVA

               What is Java?

                         Java is a programming Language which is developed by
               Sun-Microystem in 1995.

                         Java is a Programming Language and a platform for building
               different types of applications and websites.

                         Java is a high level,robust,secured and object-oriented Programming
               language.

                  Simply,"JAVA IS A PROGRAMMING LANGUAGE AND PLATFORM 
             FOR BUILDING WEBSITES AND APPLICATIONS".

             What is Platform?

                 Any hardware or software environment in which a program 

               runs, is known as a platform. Since Java has its own runtime environment

              (JRE) and API, it is called platform.

               What is JVM?

                       A Java virtual machine (JVM) is an abstract computing machine that

             enables a computer to run a Java program. There are three notions of the  

           JVM: specification, implementation and instance.

                    The specification is a document that formally describes what is required

            of a JVM implementation.

                     What is JDK? 
                  The Java Development Kit (JDK) is a software development environment

           used for developing Java applications and applets. It includes the Java Runtime 

         Environment (JRE), an interpreter/loader (java), a compiler (javac), an archiver (jar),

         a documentation generator (javadoc) and other tools needed in Java development.

 

              What is JRE?

                 
                       The Java Runtime Environment (JRE) is a set of software tools for
              development of Java applications. It combines the Java Virtual Machine (JVM),
             platform core classes and supporting libraries. JRE is part of the Java Development
             Kit (JDK), but can be downloaded separately.


                    What is Interpreter in JAVA?
                 A Java interpreter executes lines of byte code as commands to be executed. 
              The byte code is executed. The JVM takes the byte code and generates machine code.
              The byte code is compiled to machine code, and the machine code is executed.

 
             What is archiver (Jar) in JAVA?
                 File archive, data compression. Extended from. ZIP. In software, 
            JAR (Java Archive) is a package file format typically used to aggregate many Java
          class files and associated metadata and resources (text, images, etc.) into one file to
          distribute application software or libraries on the Java platform.    


             What is JAVADOC in java?
               Javadoc is a documentation generator created by Sun Microsystems for the
             Java language (now owned by Oracle Corporation) for generating API documentation
             in HTML format from Java source code.  


           How this all Actually Works?

                            firstly java source code is converted into Bytecode file by the translator 

                 named  “Compiler”. 

                          The byte code file gets name with .class extension and javac (java compiler) 

                is the tool to compile the .java file.

                Then,

                        java is a tool use to invoke Java Interpreter “JVM”. Now, the work of JVM starts.     

          When JVM invoke,

                      1. a subprogram in JVM called Class loader (or system class loader) starts and 

               load the bytecode into OS memory( or RAM).

                     2. another subprogram Bytecode Verifier verify and ensure that the code do not 

               violate the security rules. That’s why the java program is much secured and virus free.

                    3. Then last subprogram Execution Engine finally converts bytecodes into 

             machine  code. The name of that engine are in use today is JIT Just In Compiler.

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