java - Eclipse doesn't find javax.swing

Question

Eclipse cant find the import javax.swing.JOptionPane

Where is it located and how can i include it?

import javax.swing.JOptionPane;

Answer 1

1. There must be an installed (and selected) JDK in Eclipse:

   Window > Preferences > Java > Installed JREs   
   

2. The project must be configured to use that JDK:

   Project > Properties > Java Build Path > Libraries
   

   there should be an entry like "JRE System Library [JDK7]" in the list. If not press:

   Add Library... > JRE System Library
   

3. The project should have been created as a "Java Project":

   Project > Properties > Builders
   

   should include "Java Builder"