What does the class class [B represents in Java?

Those are arrays of primitives ([B == byte[], [C == char, [I == int). [Lx; is an array of class type x.

For a full list:

[Z = boolean
[B = byte
[S = short
[I = int
[J = long
[F = float
[D = double
[C = char
[L = any non-primitives(Object)

Also see the Javadoc for Class.getName.