I could not get this to run with the JDK you pointed to, the window would close with a java error.
I could run it with the JRE (Java Runtime Environment) from here:
https://www.oracle.com/java/technologies/javase-jre8-downloads.html
Get the Windows x64 one (if you have win 10 64-bit)
Win 10 has screwed up associating JAR files with Java. Try instead creating a shortcut to your java.exe file (in C:\Program Files\Java\jre1.8.0_261\bin). Put the shortcut in the same folder as the .jar file. Then right click on the shortcut, select Properties. On the Shortcut tab, add this to the very end of the Target line:
-jar theme-creator-v2_0_1.jar
And change 'Start In' to the path where the JAR file is.
Then double click the shortcut to run Theme Creator.