You could call quit, which would exit MATLAB entirely. If you were within a function, you could call return to leave the function.
Otherwise you cannot exit two nested loops. You can, however, set a flag that indicates you want to exit the outer loop and have the outer loop test it.
done_this_stuff = false;
for K = ...
for J = ...
if ...
done_this_stuff = true;
break
end
...
end
%now we are in just the outer loop
if done_this_stuff
break
end
...
end
