There is no straightforward representation of a class that is an array. (for instance java doesn't use java.lang.String[] in the class file) So when an array needs to be referenced, it represented by the 'signature' version of the class name. The [ bracket means it's an array, the LXXX; means it's an object reference of type XXX.
这种东西叫做描述符 有方法描述符和字段描述符具体在《java虚拟机规范》中有详细介绍，摘录如下：4.3.2 Field Descriptors A field descriptor represents the type of a class, instance, or local variable. It is a series of characters generated by the grammar: FieldDescriptor: FieldType ComponentType: FieldType FieldType: BaseType ObjectTypeArrayType BaseType: B CDFIJSZ ObjectType:L <classname> ; ArrayType:[ ComponentTypeThe characters of BaseType, the L and ; of ObjectType, and the [ of ArrayType are all ASCII characters. The <classname> represents a fully qualified class or interface name. For historical reasons it is encoded in internal form (§4.2). The interpretation of the field types is as shown in Table 4.2.BaseType Character Type Interpretation B byte signed byte C char Unicode character D double double-precision floating-point value F float single-precision floating-point value I int integer J long long integer L<classname>; reference an instance of class <classname> S short signed short Z boolean true or false [ reference one array dimension For example, the descriptor of an instance variable of type int is simply I. The descriptor of an instance variable of type Object is Ljava/lang/Object;. Note that the internal form of the fully qualified name for class Object is used. The descriptor of an instance variable that is a multidimensional double array, double d[][][];is [[[D4.3.3 Method Descriptors A method descriptor represents the parameters that the method takes and the value that it returns: MethodDescriptor: ( ParameterDescriptor* ) ReturnDescriptorA parameter descriptor represents a parameter passed to a method:ParameterDescriptor: FieldTypeA return descriptor represents the type of the value returned from a method. It is a series of characters generated by the grammar:ReturnDescriptor: FieldType VThe character V indicates that the method returns no value (its return type is void). A method descriptor is valid only if it represents method parameters with a total length of 255 or less, where that length includes the contribution for this in the case of instance or interface method invocations. The total length is calculated by summing the contributions of the individual parameters, where a parameter of type long or double contributes two units to the length and a parameter of any other type contributes one unit.For example, the method descriptor for the method Object mymethod(int i, double d, Thread t)is (IDLjava/lang/Thread;)Ljava/lang/Object;Note that internal forms of the fully qualified names of Thread and Object are used in the method descriptor. The method descriptor for mymethod is the same whether mymethod is a class or an instance method. Although an instance method is passed this, a reference to the current class instance, in addition to its intended parameters, that fact is not reflected in the method descriptor. (A reference to this is not passed to a class method.) The reference to this is passed implicitly by the method invocation instructions of the Java virtual machine used to invoke instance methods.
第一行表示 ResultSet 类型第二行你也写错了，开头应该还有个左括号。
第二行是个方法描述，表示：int ???(FileDescriptor x, byte[] y, int a, int b, int c) 的方法参考：JVM Specification 4.3.2 和 4.3.3 节
http://java.sun.com/docs/books/jvms/first_edition/html/ClassFile.doc.html#14152
有方法描述符和字段描述符具体在《java虚拟机规范》中有详细介绍，摘录如下：4.3.2 Field Descriptors
A field descriptor represents the type of a class, instance, or local variable. It is a series of characters generated by the grammar:
FieldDescriptor:
FieldType ComponentType:
FieldType FieldType:
BaseType
ObjectTypeArrayType
BaseType:
B
CDFIJSZ ObjectType:L <classname> ; ArrayType:[ ComponentTypeThe characters of BaseType, the L and ; of ObjectType, and the [ of ArrayType are all ASCII characters. The <classname> represents a fully qualified class or interface name. For historical reasons it is encoded in internal form (§4.2).
The interpretation of the field types is as shown in Table 4.2.BaseType Character Type Interpretation
B byte signed byte
C char Unicode character
D double double-precision floating-point value
F float single-precision floating-point value
I int integer
J long long integer
L<classname>; reference an instance of class <classname>
S short signed short
Z boolean true or false
[ reference one array dimension For example, the descriptor of an instance variable of type int is simply I. The descriptor of an instance variable of type Object is Ljava/lang/Object;. Note that the internal form of the fully qualified name for class Object is used. The descriptor of an instance variable that is a multidimensional double array,
double d[][][];is [[[D4.3.3 Method Descriptors
A method descriptor represents the parameters that the method takes and the value that it returns: MethodDescriptor:
( ParameterDescriptor* ) ReturnDescriptorA parameter descriptor represents a parameter passed to a method:ParameterDescriptor:
FieldTypeA return descriptor represents the type of the value returned from a method. It is a series of characters generated by the grammar:ReturnDescriptor:
FieldType
VThe character V indicates that the method returns no value (its return type is void).
A method descriptor is valid only if it represents method parameters with a total length of 255 or less, where that length includes the contribution for this in the case of instance or interface method invocations. The total length is calculated by summing the contributions of the individual parameters, where a parameter of type long or double contributes two units to the length and a parameter of any other type contributes one unit.For example, the method descriptor for the method
Object mymethod(int i, double d, Thread t)is (IDLjava/lang/Thread;)Ljava/lang/Object;Note that internal forms of the fully qualified names of Thread and Object are used in the method descriptor.
The method descriptor for mymethod is the same whether mymethod is a class or an instance method. Although an instance method is passed this, a reference to the current class instance, in addition to its intended parameters, that fact is not reflected in the method descriptor. (A reference to this is not passed to a class method.) The reference to this is passed implicitly by the method invocation instructions of the Java virtual machine used to invoke instance methods.