How to check the JDK version used for compiling a java class

You can use javap command to find the compiled version of a class. javap (Java Class File Disassembler) tool is a tool provided with JDK to disassemble class files.

Unix:

Open a terminal and change the working directory to the place where your class is located.

javap -verbose HelloWorld.class| grep "major"

Windows:

Open a command prompt and change the working directory to the place where your class is located.
javap -verbose HelloWorld.class | findstr "major" 

E.g.: 

 Following is the mapping between the major version and the relevant JDK version.

Major Version	Comipled JDK version
46	1.2
47	1.3
48	1.4
49	5
50	6
51	7
52	8