How to Edit a file form terminal?

Step 1 : Navigate to the parent directory.

Step 2 : Enter vim <filename.java>

Step 3 : Press " I " to edit the file.

Step 4 : After inserting your changes press "Esc" key.

Step 5 : Then press " :wq "
             
              where w - for save the changes and
                         q - for quit.