Eclipse Hover Tips
Using Hover Tips
The Java editor includes various types of hover tips, which provide additional information about the element the mouse pointer is hovering over. All related hover tips in the Java editor can be configured through the Hovers page in the preferences (search for "hover" in the search box).
When the mouse pointer is moved over a class in the Java editor, it will display the Java documentation related to that class.
When the mouse pointer is moved over a method in the Java editor, it will display the Java documentation related to that method.