refer url: link

Examples:

 String.class.getName()
     returns "java.lang.String"
 byte.class.getName()
     returns "byte"
 (new Object[3]).getClass().getName()
     returns "[Ljava.lang.Object;"
 (new int[3][4][5][6][7][8][9]).getClass().getName()
     returns "[[[[[[[I"

在我的代码中出现如下信息：

obj : [B@34be51e8
classname : [B

a single [ means an array of

L followed by a fully qualified class name (e.g. java/lang/Object) is the class name terminated by semicolon ;

so [Ljava.lang.object; means Object[]

class [B

class [Lcom.sun.mail.imap.IMAPMessage;

class [C

class [I

class [Ljava.lang.Object;

[B is array of primitive byte

[C is array of primitive char

[I is array of primitive int

[Lx is array of type x

Here is the entire list: link on SOF

B - byte
C - char
D - double
F - float
I - int
J - long
Lfully-qualified-class; - between an L and a ; is the full class name, using / as the delimiter between packages (for example, Ljava/lang/String;)
S - short
Z - boolean
[ - one [ for every dimension of the array
(argument types)return-type - method signature, such as (I)V, with the additional pseudo-type of V for void method