In the Java editor press Ctrl + Space on code to complete. This opens a list of available code completions. Some tips for using code assist are listed in the following paragraph:
You can use the mouse or the keyboard (Up Arrow, Down Arrow, Page Up, Page Down, Home, End, Enter) to navigate and select lines in the list.
If you select a line in the content assist list, you can view Javadoc information for that line.
Clicking or pressing Enter on a selected line in the list inserts the selection into the editor.
You can access specialized content assist features inside Javadoc comments.
Configure the behavior of the content assist in the Java > Editor > Code Assist preference page.
Java development tools (JDT)
Java editor preferences