How to know JDK version from within Java code

Question

How to know JDK version from within Java code

Answer 1

I presume you mean just the Java version, in which case try this:

String version = System.getProperty("java.version");

Answer 2

Since java 9

System.out.println(Runtime.version());

Prints something like 17.0.2+8-86

or if you need more

System.out.println("Java Feature Version = " + Runtime.version().feature());
System.out.println("Java Interim Version = " + Runtime.version().interim());
System.out.println("Java Update Version = " + Runtime.version().update());
System.out.println("Java Version Build = " + Runtime.version().build().map(String::valueOf).orElse("Unknown"));
System.out.println("Java Version Pre-Release Info = " + Runtime.version().pre().orElse("N/A"));

Prints

Java Feature Version = 17
Java Interim Version = 0
Java Update Version = 2
Java Version Build = 8
Java Version Pre-Release Info = N/A

Answer 3

Relying on the java.version string for anything else than showing to a human is fragile and will break if running on another Java implementation.

The only reliable way programatically is to use reflection to carefully ask if a given facility is available, and then select the appropriate code accordingly.

• Jesse Barnum: Can you give an example of when this would fail?
• Thorbjørn Ravn Andersen: @Jesse, I'd rather put it the other way around. What rule would you set up for analyzing the java.version string?
• Thorbjørn Ravn Andersen: @Jesse, I was unaware of this property. I can, however, not see from a quick look in the JLS that it is guaranteed to be present and containing a valid number. Perhaps you know where it says so?
• Thorbjørn Ravn Andersen: @Jesse, the crucial question here if this is for Hotspot-based JVM's only. I cannot immediately tell.
• Mark Jeronimus: Don't use Float.valueOf like @JesseBarnum. This failed for me because 1.8>=1.8 returned false for me, due to round-off errors. Use .compareTo("1.8")>=0 instead.

Answer 4

If you need to know the bit version(32bit or 64 bit) as well, and you are running a hotSpot JVM, you can try this code:

System.getProperty("sun.arch.data.model")

No grantee that it will work for other Java implementaions rather than hotSpot.