Breakpoints are crossed out, how can I make them valid?

Screenshot of the 'skip all breakpoints' in eclipse.

When you click on 'skip all breakpoints'(which is selected), everything will become normal

The shortcut key for placing a breakpoint in Eclipse (Ctrl + Shift + B) is quite similar to the one that skips all the breakpoint (Ctrl + Alt + B). Hence, if a "skip all breakpoints" condition is to be cancelled, it can be achieved by pressing "Ctrl + Alt + B" again.

There is a menu entry you have discovered for yourself that toggles the skipping of all breakpoints. There is also an icon for this in the "Breakpoints" View, and there may be a hot-key defined as well, all of which you may have triggered by accident.

Take a look at the Run -> Skip All Breakpoints.