File structure

Once compiled, text .java files become .class files and can be executed by the JVM straight away.

Here is their structure according to the official documentation:

ClassFile {
    u4 magic;
    u2 minor_version;
    u2 major_version;
    u2 constant_pool_count;
    cp_info constant_pool[constant_pool_count-1];
    u2 access_flags;
    u2 this_class;
    u2 super_class;
    u2 interfaces_count;
    u2 interfaces[interfaces_count];
    u2 fields_count;
    field_info fields[fields_count];
    u2 methods_count;
    method_info methods[methods_count];
    u2 attributes_count;
    attribute_info attributes[attributes_count];
}

The magic value that's used in this case is a hexademical DWORD 0xCAFEBABE. The other fields are self-explanatory.

The most common way to release a more complex project is to build a JAR file that contains multiple compiled modules, as well as auxiliary metadata files such as MANIFEST.MF. JAR files follow the usual ZIP archive format and can be extracted using any...