Difference between JDK, JRE and JVM

Another aspect worth mentioning :

jdk (java development kit)

you will need it for development purposes like the name suggest ,,

example : a software company will have jdk install in their computer because they will need to devlop new software which include compile and run their java programs as well.

so we can say that jdk = jre+ jvm .

jre (java run-time environment)

It;s needed to run java programs ,, you can't compile java programs with it .

Example : a regular computer user who wants to is run some online games then will need jre in his system to run java programs.

jvm (java virtual machine)

As you might know it run the bytecodes . It make java platform independent because it executes the .class file which you get after you compile the java program no matter if you compile it on windows,mac or linux.

open jdk

well like i said above .... now jdk is made by different company ,,, one of them which happens to be an open source and free for public use is openjdk... while some others are Oracle Corporation's JRockit JDK or ibm jdk...

However they all might appear same to general user..

Conclusion

If you are a java program you will need jdk in your system and this package will include jre and jvm as well but if you are normal user who like to play online games then you will only need jre and this package will not have jdk in it.

In other words jdk is grandfather jre is father and jvm is their son.