Just to show how a class file looks, here is the output of the jdisco program. It shows all the fields in the class file. Each operand of an instruction is shown in hexadecimal form.
Reading from file example.class...
magic_number: cafebabe
minor_version: 3
major_version: 45
constant_pool_count: 76
constant_pool[1]: (CONSTANT_Class_info)
tag: 7
name_index: 2
constant_pool[2]: (CONSTANT_Utf8_info)
tag: 1
length: 16
string: java/lang/Object
constant_pool[3]: (CONSTANT_Class_info)
tag: 7
name_index: 4
constant_pool[4]: (CONSTANT_Utf8_info)
tag: 1
length: 7
string: example
constant_pool[5]: (CONSTANT_Methodref_info)
tag: 10
class_index: 1
name_and_type_index: 6
constant_pool[6]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 7
descriptor_index: 8
constant_pool[7]: (CONSTANT_Utf8_info)
tag: 1
length: 6
string: <init>
constant_pool[8]: (CONSTANT_Utf8_info)
tag: 1
length: 3
string: ()V
constant_pool[9]: (CONSTANT_Utf8_info)
tag: 1
length: 8
string: <clinit>
constant_pool[10]: (CONSTANT_Utf8_info)
tag: 1
length: 4
string: Code
constant_pool[11]: (CONSTANT_Utf8_info)
tag: 1
length: 13
string: ConstantValue
constant_pool[12]: (CONSTANT_Utf8_info)
tag: 1
length: 10
string: Exceptions
constant_pool[13]: (CONSTANT_Class_info)
tag: 7
name_index: 14
constant_pool[14]: (CONSTANT_Utf8_info)
tag: 1
length: 9
string: pcrterror
constant_pool[15]: (CONSTANT_Utf8_info)
tag: 1
length: 14
string: ThrowFunResExc
constant_pool[16]: (CONSTANT_Methodref_info)
tag: 10
class_index: 13
name_and_type_index: 17
constant_pool[17]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 15
descriptor_index: 8
constant_pool[18]: (CONSTANT_Class_info)
tag: 7
name_index: 19
constant_pool[19]: (CONSTANT_Utf8_info)
tag: 1
length: 4
string: pcio
constant_pool[20]: (CONSTANT_Utf8_info)
tag: 1
length: 7
string: pcwrite
constant_pool[21]: (CONSTANT_Utf8_info)
tag: 1
length: 9
string: pcwriteln
constant_pool[22]: (CONSTANT_Utf8_info)
tag: 1
length: 4
string: (F)V
constant_pool[23]: (CONSTANT_Utf8_info)
tag: 1
length: 5
string: (FI)V
constant_pool[24]: (CONSTANT_Utf8_info)
tag: 1
length: 6
string: (FII)V
constant_pool[25]: (CONSTANT_Utf8_info)
tag: 1
length: 4
string: (Z)V
constant_pool[26]: (CONSTANT_Utf8_info)
tag: 1
length: 5
string: (ZI)V
constant_pool[27]: (CONSTANT_Utf8_info)
tag: 1
length: 4
string: (C)V
constant_pool[28]: (CONSTANT_Utf8_info)
tag: 1
length: 5
string: (CI)V
constant_pool[29]: (CONSTANT_Utf8_info)
tag: 1
length: 4
string: (I)V
constant_pool[30]: (CONSTANT_Utf8_info)
tag: 1
length: 5
string: (II)V
constant_pool[31]: (CONSTANT_Utf8_info)
tag: 1
length: 21
string: (Ljava/lang/String;)V
constant_pool[32]: (CONSTANT_Utf8_info)
tag: 1
length: 22
string: (Ljava/lang/String;I)V
constant_pool[33]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 34
constant_pool[34]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 22
constant_pool[35]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 36
constant_pool[36]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 23
constant_pool[37]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 38
constant_pool[38]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 24
constant_pool[39]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 40
constant_pool[40]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 25
constant_pool[41]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 42
constant_pool[42]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 26
constant_pool[43]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 44
constant_pool[44]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 27
constant_pool[45]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 46
constant_pool[46]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 28
constant_pool[47]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 48
constant_pool[48]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 29
constant_pool[49]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 50
constant_pool[50]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 30
constant_pool[51]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 52
constant_pool[52]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 31
constant_pool[53]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 54
constant_pool[54]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 20
descriptor_index: 32
constant_pool[55]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 56
constant_pool[56]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 21
descriptor_index: 8
constant_pool[57]: (CONSTANT_Utf8_info)
tag: 1
length: 9
string: pcread_fl
constant_pool[58]: (CONSTANT_Utf8_info)
tag: 1
length: 9
string: pcread_ch
constant_pool[59]: (CONSTANT_Utf8_info)
tag: 1
length: 10
string: pcread_int
constant_pool[60]: (CONSTANT_Utf8_info)
tag: 1
length: 8
string: pcreadln
constant_pool[61]: (CONSTANT_Utf8_info)
tag: 1
length: 3
string: ()F
constant_pool[62]: (CONSTANT_Utf8_info)
tag: 1
length: 3
string: ()I
constant_pool[63]: (CONSTANT_Utf8_info)
tag: 1
length: 3
string: ()I
constant_pool[64]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 65
constant_pool[65]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 57
descriptor_index: 61
constant_pool[66]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 67
constant_pool[67]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 58
descriptor_index: 62
constant_pool[68]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 69
constant_pool[69]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 59
descriptor_index: 63
constant_pool[70]: (CONSTANT_Methodref_info)
tag: 10
class_index: 18
name_and_type_index: 71
constant_pool[71]: (CONSTANT_NameAndType_info)
tag: 12
name_index: 60
descriptor_index: 8
constant_pool[72]: (CONSTANT_Utf8_info)
tag: 1
length: 4
string: main
constant_pool[73]: (CONSTANT_Utf8_info)
tag: 1
length: 22
string: ([Ljava/lang/String;)V
constant_pool[74]: (CONSTANT_String_info)
tag: 8
string_index: 75
constant_pool[75]: (CONSTANT_Utf8_info)
tag: 1
length: 12
string: Hello, world
acces_flags: <no flags>
this_class: 3
super_class: 1
interfaces_count: 0
interfaces[]: <none>
fields_count: 0
fields[]: <none>
methods_count: 2
methods[0]:
acces_flags: <no flags>
name_index: 7
descriptor_index: 8
attributes_count: 1
attributes[0]:
attribute_name_index: 10 (Code)
attribute_length: 17
max_stack: 1
max_locals: 1
code_length: 5
code[]:
0 aload_0
1 invokespecial 00 05
4 return
exception_table_length: 0
exception_table[]: <none>
attributes_count: 0
attributes[]: <none>
methods[1]:
acces_flags: ACC_PUBLIC ACC_STATIC
name_index: 72
descriptor_index: 73
attributes_count: 1
attributes[0]:
attribute_name_index: 10 (Code)
attribute_length: 21
max_stack: 2
max_locals: 1
code_length: 9
code[]:
0 ldc 4a
2 invokestatic 00 33
5 invokestatic 00 37
8 return
exception_table_length: 0
exception_table[]: <none>
attributes_count: 0
attributes[]: <none>
attributes_count: 0
attributes[]: <none>
Done, closing example.class...