Show dotted lines in a JTree

In your code

...
tree.putClientProperty("JTree.lineStyle", "Angled");
...

Or from the command line

java -DJTree.lineStyle=Angled  MyApp

Other possible values :

None   
       No lines are drawn anywhere on the tree.
Angled 
       Vertical lines between nodes at the same level,
       horizontal line to child node.
Horizontal
       A single horizontal line between nodes immediately
       attached to the root node. This is the default setting.