Check java version during program load

Question

I'm looking for a way to check which java version my software is running under.

I'd like to verify during load time my software is running on at least

• NullPointerException: System.getProperty("java.version")
• arshajii: Can you finish your last sentence.
• Steve Kuo: How many duplicate answers do we need?

Answer 1

To get the java version you can use any of these depending on the version you want:

java.specification.version
java.version 
java.vm.version 
java.runtime.version 

However, note that java versions are not equivalent between operative systems. So Java 6 on OSX does not mean the same thing as Java 6 on Windows. So, I would recommend you to also get the OS where the application is running, if you wish to determine if a given feature is available:

System.getProperty("os.name")

As a general guideline, all of this stuff is in the System package. A trick I use is iterate through all the available fields to have an idea of what I can use:

import java.util.Map;
class ShowProperties {
 public static void main(String[] args) {
 for (Map.Entry<Object, Object> e : System.getProperties().entrySet()) {
 System.out.println(e);
 }
 }
}

Answer 2

Use java.version property to retrieve the jre version.

 String javaVersion = System.getProperty("java.version");
if ((!javaVersion.startsWith("1.6")) && (!javaVersion.startsWith("1.7")) && (!javaVersion.startsWith("1.8")) && (!javaVersion.startsWith("1.9")))
{
 // error
}

• Steve Kuo: You've got extra parentheses

Answer 3

You can use System.getProperty:

System.out.println(System.getProperty("java.version"));

1.7.0_21

Answer 4

java.lang.System.getProperty("java.version")