Which JRE am I using?

Question

There are two varieties of JRE available. Java VM: IBM vs. Sun.

Is there a way to know which JRE I am using through JavaScript or some Java issued command.

Answer 1

In Linux:

java -version

In Windows:

java.exe -version

If you need more info about the JVM you can call the executable with the parameter -XshowSettings:properties. It will show a lot of System Properties. These properties can also be accessed by means of the static method System.getProperty(String) in a Java class. As example this is an excerpt of some of the properties that can be obtained:

$ java -XshowSettings:properties -version
[...]
java.specification.version = 1.7
java.vendor = Oracle Corporation
java.vendor.url = http://java.oracle.com/
java.vendor.url.bug = http://bugreport.sun.com/bugreport/
java.version = 1.7.0_95
[...]

So if you need to access any of these properties from Java code you can use:

System.getProperty("java.specification.version");
System.getProperty("java.vendor");
System.getProperty("java.vendor.url");
System.getProperty("java.version");

Take into account that sometimes the vendor is not exposed as clear as Oracle or IBM. For example,

$ java version
"1.6.0_22" Java(TM) SE Runtime Environment (build 1.6.0_22-b04) Java HotSpot(TM) Client VM (build 17.1-b03, mixed mode, sharing)

HotSpot is what Oracle calls their implementation of the JVM. Check this list if the vendor does not seem to be shown with -version.