Install Java if it is not already installed
Double-click the JAR file to run it if it is an executable JAR
Open it with the Java Runtime Environment using the command line
Use `java -jar filename.jar` in Command Prompt, Terminal, or PowerShell
Open it with a file archiver such as 7-Zip, WinRAR, or WinZip to view its contents
Change the file association to open JAR files with Java
Use an IDE such as Eclipse or IntelliJ IDEA to inspect or run the JAR
Rename the file extension to `.zip` only if you need to extract its contents and the file is not meant to be executed