Java is one of the most popular programming languages in the world, used for many applications including RuneScape. In order to play RuneScape you have to install Java. This is already included in the official client and does not need a separate installation, but you will have to install it for botting clients. Before installation Java 8, make sure that you do not have any other Java versions already installed on your PC. You can download Java 8 here.
You will need to create an Oracle account in order to download it. Do not download any Java version other than 8. After installing it, you should be able to open applications with Java.
Verifying Java installation
1. Open a command prompt
2. Execute the command “java -version”
If the java version is 1.8.0_xxx then your Java installation is correct, otherwise you will have to remove all other Java versions and only after that install Java 8.