How to Check Hadoop Version
Finding the version of Hadoop that you have installed is extremely easy. You can just use the hadoop command like this:
hadoop version
If that is too easy for you then you might think about checking that file names and file paths for your Hadoop installation. You can also find hints there but this is generally going to be completely unnecessary.
From Java Code
You can also check the version of Hadoop being used from within your Java code. The following snippet will print out the version in use to the terminal. You could also pass this variable to whatever function you want.
String ver = org.apache.hadoop.util.VersionInfo.getVersion();
System.out.println(ver);