JavaCheck.jar is a Java file shipped with the Minecraft launcher. This isn't problematic for most, but those that prefer to use newer versions of Java, or mods that are incapable with older versions of Java, can't modify their profiles to use the version that isn't defaulted for that Java version.
Thankfully, it's easy to bypass this by deleting this file, but is reinstalled after every update, so in the long run, this could be a useful application, especially for those rocking the beta launcher (like I do).

Download the .exe file found in the latest release, and place it somewhere memorable (such as your desktop). This app will only run with manual execution, so you'll be required to run it after every update.

Run DeleteJavaCheckRewritten.exe, and if there's no issues, the file should be deleted
Another thing to note is that this file (javacheck.jar) will most likely be permanently deleted, so remember to run the right version of Java on newer installations

• For the current moment, new files are in DeleteJavaCheckRewritten to prevent clashes and data loss. This'll be fixed later

• None currently planned