2 Added warning about PE
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Java bytecode files can be identified by their magic number: 0xCAFEBABE at the beginning of the file. Also the standard naming convention is to have these files' names end in .class.

However, @hexafraction warns in a comment: "Java classfiles would not have their magic number or file extension visible when packed into a .exe PE, except if they were unpacked (assuming that they're just packed in the first place, and not recompiled to machine code)"

Java bytecode files can be identified by their magic number: 0xCAFEBABE at the beginning of the file. Also the standard naming convention is to have these files' names end in .class.

Java bytecode files can be identified by their magic number: 0xCAFEBABE at the beginning of the file. Also the standard naming convention is to have these files' names end in .class.

However, @hexafraction warns in a comment: "Java classfiles would not have their magic number or file extension visible when packed into a .exe PE, except if they were unpacked (assuming that they're just packed in the first place, and not recompiled to machine code)"

1
source | link

Java bytecode files can be identified by their magic number: 0xCAFEBABE at the beginning of the file. Also the standard naming convention is to have these files' names end in .class.