Nanyang Technological University: "Downloading and Installing JDK"
If you are comfortable with installing software on your machine, or if you'd prefer not to use an online IDE, you may refer to this page, which discusses how to download and install the latest version of JDK. Even so, we recommend using an online IDE, as described in the section above, for writing your first simple programs for this course and getting used to Java.
If you do decide to install Java on your machine, read the instructions carefully to set the "classpath" mentioned in Step 3. Once JDK has been installed, you can write a simple Java program using an editor such as notepad and run it from a command prompt. Alternatively, Java programs can be written using an Integrated Development Environment (IDE) such as NetBeans, described below.