Learning the java language can be tough if you follow wrong documents. It's always best to follow the official tutorials provided by Oracle. They have provided all the Java Tutorials which are present on its website in ePub and mobi format.
You can download all of them at
http://www.oracle.com/technetwork/java/javase/java-tutorial-downloads-2005894.html
Check for the latest version of above page. Currently the link contains docs for Java8. It will prompt you the link for new version once later versions are released.