For JAVA :
Single line comment:
// this is a single line comment
To comment: Ctrl + Shift + C
To uncomment: Press again Ctrl + Shift + C
Multiple line comment:
/* .........
.........
......... */
First, select all the lines that you want to comment/uncomment then,
To comment: Ctrl + Shift + C
To uncomment: Press again Ctrl + Shift + C
I hope, this will work for you!