How to properly set up Java/Selenium configuration to run automated tests?
You will have to download the "Selenium Client & WebDriver Language Bindings" for Java from Selenium Downloads. You can download directly by clicking the link here.
Include all the JAR files that are present in the downloaded ZIP file. To include multiple JARs in Java classpath, you can check the link here.
The selenium-server-standalone JAR is required if you are running your tests locally. Executing the command java -jar selenium-server-standalone-2.48.2.jar will start a Selenium server, which required to launch Selenium tests locally. You need not use it, if you are running tests on BrowserStack.
Would also recommend using an IDE for Java. The most commonly recommended ones are IntelliJ Idea, Eclipse, and Netbeans.