This problem happens intermittently for different libraries and different projects. When trying to import a library, the package will be recognized, but the class name can\'
I found the following answer from @jossef-harush and @matt-leidholm useful from another link
Integer for example) and press ALT + ENTER (or click the light bulb icon)Setup JDK from the intentions menu
Configure
JDK path was incorrect (pointed on /opt/jdk1.7.0_51 instead of /opt/jdk1.7.0_65)
JDK path 
