How to comment a block in Eclipse?

Ctrl-/ to toggle "//" comments and Ctrl-Shift-/ to toggle "/* */" comments. At least for Java, anyway - other tooling may have different shortcuts.

Ctrl-\ will remove a block of either comment, but won't add comments.

Note: As for Eclipse CDT 4.4.2, Ctrl-Shift-/ will not uncomment a "/* */" block comment. Use Ctrl-Shift-\ in that case.

EDIT: It's Ctrl on a PC, but on a Mac the shortcuts may all be Cmd instead. I don't have a Mac myself, so can't easily check.

There are two possibilities:

Every line prepended with //

ctrl + / to comment
ctrl + \ to uncomment

Note: on recent eclipse cdt, ctrl + / is used to toggle comments (and ctrl + \ has no more effect)

Complete block surrounded with block comments /*

ctrl + shift + / to comment
ctrl + shift + \ to remove

For Eclipse Editor

For Single Line (Toggle Effect)

Comment : Ctrl+Shift+c

Uncomment: Ctrl+Shift+c

For Multiple Lines (Toggle Effect) (Select the lines you want to comment)

comment : Ctrl+Shift+c

Uncomment: Ctrl+Shift+c

It is for all html , css , jsp , java . It gives toggle effect.