Version check of JRE in app

Question

Hi,
I want my application(not web-based or whatever) to know which version of JRE the client is using.
The thing is, I know it's with System.getProperty("java.version"), but I want to compare it with another version string in the application. The user JRE version must be equal or greater than the version.
For ex: if the application was build with 1.4.0_01 and the user has 1.4.1_01, it must be accepted, but not if it's 1.3.x or whatever.
I've done a temporary method with a string tokenizer to evaluate each number and see if it's up to date, but is there a method or utility already there that checks if the version is equal or better?
Thx
Frank

Answer 1

i just have the same kind of problem. even more so, since i noticed that there are possibly more non-numeric characters in the version string, like "1.4.0-beta3", so even using a StringTokenizer splitting the string by the "." and "_" characters (like i think you do, from the example in your posting), the last part would cause a NumberFormatException in many cases.
of course you could include the "-" character in the tokenizer and drop the last token, but you can never be sure if there won't be version strings like "1.5.2b" or such in the future. a workaround here would be taking each character from the token, check if it's a number, add it to another string if so, or stop if it's a non-numeric character or the end of the string. then you could transform the constructed string into an integer and compare it to the corresponding part of the required version.
however, this seems to be quite a lot of not too elegant trickery which i'm not even sure will work in all cases, and it's definitely too much work for a simple version check. anyway, i haven't found any other way yet, too :/ if anyone knows, please let me know...