Skip to main content

JDK(Java Development Kit) What and Why?

on

You will get a memorable calculation among three:

  • JDK(Java Development Kit)
  • JRE(Java Runtime Environment)
  • JVM(Java Virtual Machine)

Let's take a sip of JVM first.
JVM(Java Virtual Machine) came into existence to provide Platform Independence to Java.

When Java compiler generates Bytecode, OS doesn't know anything about Bytecode because it is Java's self-created code. OS cannot execute it.
So, Java needed a Machine to execute it's Bytecode, to fulfill this need  JVM came. JVM provides an environment for the survival of Bytecode.

Remember that, JVM is platform dependent i.e. for every OS there is different JVM.

But there is a difference in old technologies and Java. Before Java, other technologies had not been allowed to make their compiler for every OS. Like Microsoft had not been allowed Linux or Unix to develop their Visual Basic's compiler.  But SunMicrosystem made this possible. SunMicrcosystem first developed a unique compiler(javac) and allow any OS to develop JVM.

Now JVM making is damn easy rather compiler. Sunmicrosystem provides JVM making code to OS vendors. OS vendor just added their OS-specific code and a working JVM is ready, Really how easy is that.
Note: Because  Sunmicrosystem develops and unique compiler i.e. there is only one compiler for java which produces unique bytecode so the code to develop Machine (JVM) which handles bytecode will be unique i.e. code which develop JVM would also be unique.

But from JDK 1.5, there is a concept of JRE(Java Runtime Environment).
In JRE, they just provide readymade virtual machine i.e. OS vendor has no more need to include OS specific code, It has already developed for each OS and uploaded on Oracle's official website. we only need to go on website, download JRE and start code.

JRE = JVM + 20% code of specific OS


JDK = JRE + Development tools
    • JRE = JVM + 20% code of specific OS
      • Development tools: java, javac, javap, javaw etc.

    Development tools:
    JAVA already provide some basic tools which are very useful for some basic operations like compilation, run, document generation etc. I am not going in detail here for those. These are:
    • java
    • javac
    • javap
    • javaw etc..

    Comments

    Post a Comment

    suggestions

    Popular posts from this blog

    Why "F" and "L" suffix | (10.0F, 10L)

    on
    Let us take it this way, We will create their needs. So we will get why they are needed. Try to guess, which functions will be executed in the following program: public class MyClass {     public static void main(String args[]) {         MyClass obj = new MyClass();         obj.fun1(10);     }     void fun1(byte val){         System.out.println(val);     }     void fun1(int val){         System.out.println(val);     }     void fun1(float val){         System.out.println(val);     }     void fun1(long val){         System.out.println(val);     }     } It seems like every method is capable to run this program because 10 is still literal because It has no data type. Before Java, In previous technologies, this scenario gave an ambiguity error. But Java solves this problem by removing the concepts of literals. It means Java provide a data type immediately when these born. So here 10 is no more literal. Java provides Integer data type for it. So now it is of Integer t
    7 comments
    Read more

    only large files upload on S3 | Ruby On Rails

    on
    models/attachment.rb class Attachment < ApplicationRecord after_initialize :set_storage private def set_storage # larger that 5mb file would be upload on s3 if file . blob . byte_size > 5_000_000 Rails . application . config . active_storage . service = :amazon else Rails . application . config . active_storage . service = :local end end # end of private end
    Post a Comment
    Read more

    Typecasting | How is Long to Float Conversion possible?

    on
    We will take a brief description of Typecasting and will try to do focus on Log to Float Conversion. Typecasting: Assigning a value of one data type to another. When we assign a value of smaller data type to a bigger one. it is called Widening. Java did this conversion automatically as they are compatible. As shown in the following figure: One another kind of conversion, when automatic conversion not possible i.e. when they are not compatible is Shortening. It will be just opposite of above and diagram will be reversed. How is Long to Float Conversion possible? If we look carefully at the diagram, there is one conversion which looks questionable is Long(8 bytes) to Float(4 bytes) conversion. It looks like data lossy conversion. Actually, Type conversion does two things: Either change in range or change in behavior or both. Change in Range: short a = 3456 // this value can be varied within the range of -32768 to 32767 int b = a // now this value can be varied wi
    4 comments
    Read more