Java class file: Difference between revisions

Revision as of 10:13, 29 December 2024

Latest revision as of 18:11, 7 July 2025

(3 intermediate revisions by 3 users not shown)

Line 34:

===Sections===

There are 10 basic sections to the Java class file structure:

* '''[[Magic number (programming)|Magic Number]]''': <code>0xCAFEBABE</code>

* '''Version of Class File Format''': the minor and major versions of the class file

* '''Constant Pool''': Pool of constants for the class

Line 96:

| rowspan="2" | u2

| rowspan="2" | major version number of the class file format being used.<ref>{{Cite web|url=https://docs.oracle.com/javase/specs/jvms/se23/html/jvms-4.html#jvms-4.1-200-B.2|title = Table 4.1-A. class file format major versions}}</ref><br />

Java SE 25 = 69 (0x45 hex),<br />

Java SE 24 = 68 (0x44 hex),<br />

Java SE 23 = 67 (0x43 hex),<br />

Line 231 ⟶ 232:

|}

===Representation inof a C-likeclass programming languagefile===

The following is a representation of a {{mono|.class}} file as if it were a C-style struct.

Since [[C (programming language)|C]] doesn't support multiple variable length arrays within a struct, the code below won't compile and only serves as a demonstration.

<syntaxhighlight lang="ccpp">

struct Class_File_FormatClassFileFormat {

u4 magic_numbermagicNumber;

u2 minor_versionminorVersion;

u2 major_versionmajorVersion;

u2 constant_pool_countconstantPoolCount;

ConstantPoolInfo[constantPoolCount - 1] constantPool;

cp_info constant_pool[constant_pool_count - 1];

u2 access_flagsaccessFlags;

u2 this_classthisClass;

u2 super_classsuperClass;

u2 interfaces_countinterfacesCount;

u2[interfacesCount] interfaces;

u2 interfaces[interfaces_count];

u2 fields_countfieldsCount;

FieldInfo[fieldsCount] fields;

field_info fields[fields_count];

u2 methods_countmethodsCount;

MethodInfo[methodsCount] methods;

method_info methods[methods_count];

u2 attributes_countattributesCount;

AttributeInfo[attributesCount] attributes;

attribute_info attributes[attributes_count];

}

</syntaxhighlight>