Question

How do I determine the version of the Java Virtual Machine from an applet or application?

Answer

You can determine the JVM version and vendor by accessing system properties. If you're not familiar with Java Properties, a Properties object contains a mapping between string keys and string values. The JVM version is stored in the system properties object, accessible via the static System.getProperties() method. The Java API documentation lists the following keys and descriptions

Key	Description of Associated Value
java.version	Java Runtime Environment version
java.vendor	Java Runtime Environment vendor
java.vendor.url	Java vendor URL
java.home	Java installation directory
java.vm.specification.version	Java Virtual Machine specification version
java.vm.specification.vendor	Java Virtual Machine specification vendor
java.vm.specification.name	Java Virtual Machine specification name
java.vm.version	Java Virtual Machine implementation version
java.vm.vendor	Java Virtual Machine implementation vendor
java.vm.name	Java Virtual Machine implementation name
java.specification.version	Java Runtime Environment specification version
java.specification.vendor	Java Runtime Environment specification vendor
java.specification.name	Java Runtime Environment specification name
java.class.version	Java class format version number
java.class.path	Java class path
os.name	Operating system name
os.arch	Operating system architecture
os.version	Operating system version
file.separator	File separator ("/" on UNIX)
path.separator	Path separator (":" on UNIX)
line.separator	Line separator ("\n" on UNIX)
user.name	User's account name
user.home	User's home directory
user.dir	User's current working directory

Not every JVM is guaranteed to support these properties. For example, the Microsoft JVM will return null values for a request to get the 'java.vm.vendor' property. It will, however, return a value for 'java.vendor'. It may be better to check for these values instead, to guarantee compatibility. An example of this is as follows:-

import java.util.Properties;

public class jvm_version
{
 public static void main(String args[])
 {
  Properties prop = System.getProperties();
  System.out.println ("JVM Vendor : " + prop.getProperty("java.vendor") );
  System.out.println ("JVM Version: " + prop.getProperty("java.version") );
 }
}

Simple Program To Find Java Vendor Information

import java.util.Properties;

public class jvm_version

{

public static void main(String args[])

{

Properties prop = System.getProperties();

System.out.println ("JVM Vendor : " + prop.getProperty("java.vendor") );

System.out.println ("JVM Version: " + prop.getProperty("java.version") );

}

}

Note: class jvm_version is public, should be declared in a file named jvm_version.java