I would like to get the effect like if JTabbedPane would be turned 90 degrees counterclockwise (only tabs but not the content inside tabs). What is the best way to implement that in Java?
You can specify the placement in the constructor:
http://download.oracle.com/javase/6/docs/api/javax/swing/JTabbedPane.html#JTabbedPane%28int%29
or in the setter:
http://download.oracle.com/javase/6/docs/api/javax/swing/JTabbedPane.html#setTabPlacement%28int%29