Believe that a lot of java The beginners are all stuck in JDK and JRE here , What is the difference between the two , Most of them are in the clouds . In fact, what I want to say is JDK and JRE It's not as simple as you think .
Let's give you a brief introduction Java All kinds of integrated development tools ：
JDK: Development kit
JRE:（ Running environment ） Runtime class library
JVM:java virtual machine
A small summary ：JDK contain JRE contain JVM
One 、JDK—— development environment （ The core ）
java development kit Abbreviation , intend JAVA development tool , We write documents to do PPT need office Office software , Development, of course, requires development tools , When it comes to development tools, you will surely think of Eclipse, But if you install it directly Eclipse You'll find it doesn't work It's a mistake , Only installed JDK, The environment variables and path To run successfully . I believe that many people have a deep understanding of this .
JDK It consists of three parts ,
The first part is Java Runtime environment ,JVM.
The second part is Java Base class library of , The number of this class library is still very considerable .
The third part is Java Development tools , They all help you use it better Java The sharp weapon of .
JRE—— Running environment
java runtime environment （java Runtime environment ） Abbreviation
1,1_JDK Medium JRE
Here's the picture ：jdk It contains jre, stay jre Of bin There's a... In the catalogue jvm.dll, since JRE It's the runtime environment , So where is it running ？ Must be JVM On the virtual machine . another ,jre Of lib There are some in the catalog JAVA The class library class file , It has been packed into jar file .
1.2_ the second JRE（ Independent runtime environment ）
Here's the picture , Whether it's JDK Medium JRE still JRE Since the runtime environment must have JVM. therefore JVM There are also two .
3、 ... and 、JVM—— Transformation environment
java virtuak machine （java virtual machine ） Abbreviation .
When you mention JAVA The advantages of ： A compilation , Run anywhere , To put it bluntly, cross platform is good , this JVM " .
JAVA Our compiled code will be compiled as Class file ,Class The document is in JVM Files running on ,
Only JVM Not yet class Implementation , Because it's explaining class When JVM Need to call the class library needed for interpretation lib, and jre contain lib Class library .
JVM Information related to specific operating system platform is blocked , bring Java The program only needs to be generated in Java Target code running on virtual machine （ Bytecode ）, It can run unmodified on multiple platforms .
JVM It's also a very deep knowledge , Interested children's shoes can be further studied , Only good , There is no harm in .
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