If you have JDK and Eclipse IDE, you can create a first aka hello world application.
First, you have to start Eclipse. During startup Eclipse will ask you for location of workspace directory. In this directory it will save all necessary configuration files and projects. I will use this workspace directory.
After startup right click New Java project. Type name of the project: hello world and click finish
Here we can see directory with Java sources. Everything is empty. Your application must do something, otherwise all of this would be pointless.
Code that does something is located in methods, that are in classes.
So first we must create a new class. Right click new class. Type name of your class: Application. Type name of package app and click to generate main method.
This method is a point, where your application starts. Click Finish Here instead of this todo write your code. To write something to standard output write system out println hello world.
And now you can start your first application.