Two options come to my mind to achieve your goal, but both of them require the selection of statement first.
After you select statement, press CTRL+SPACE, then type syso
and hit Enter.
Selected statement will be placed inside System.out
block:
System.out.println(statement);
Also you can prepare eclipse template (Window->Preference->Java->Editor->Content Assist->Templates), and give it some name:
System.out.println(${line_selection});${cursor}
After you select statement, press ALT+SHIFT+Z or select menu option Source->Surround With (also in context menu). Template you have created should be there so select it. Selected statement will be wrapped inside desired block of code.