How do I read a Java class file (Java bytecode)

Question

How do I view the contents of a .class file (java byte code)?

How do I open these type of files in Linux? I'm using Centos 5.8.

If you just want to view the binary or hex dump, you can use [od](http://unixhelp.ed.ac.uk/CGI/man-cgi?od) — jpm, Jan 03 '13 at 20:36

score 55 · Accepted Answer · answered Jan 03 '13 at 20:36

55

javap -c X will show the disassembly of X.class.

answered Jan 03 '13 at 20:36

NPE

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using javap X -c worked ! Thanks. – karunakar Jan 03 '13 at 23:36
I've been looking for something like this. Thanks! – Leonhard Printz Apr 18 '19 at 10:59

score 13 · Answer 2 · edited Nov 27 '14 at 14:49

13

Read bytecode

javap -v com.company.package.MainClass

To understand bytecode You can use this list of mnemonics

edited Nov 27 '14 at 14:49

Jonathan Drapeau

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answered Jan 03 '13 at 21:15

Marcin Szymczak

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+1 for the link to the online decompiler! – John Farrelly Jan 03 '13 at 22:24

score 2 · Answer 3 · edited May 23 '17 at 11:54

2

You could decompile it.

To see Java source code check some decompiler. Go search for jad.

If you want to see bytecodes, just use javap which comes with the JDK.

edited May 23 '17 at 11:54

Community

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answered Jan 03 '13 at 20:37

asgoth

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score 1 · Answer 4 · answered Jan 03 '13 at 20:35

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use javap. it's a part of the standard jdk.

answered Jan 03 '13 at 20:35

fdreger

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score 0 · Answer 5 · answered Jan 03 '13 at 20:34

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less filename.class

Not sure how it will help you, unless you can read byte code...

answered Jan 03 '13 at 20:34

KingCronus

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Geeee, I wanted to write that! But I think this would rather fit as a comment... – ppeterka Jan 03 '13 at 20:35
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+1 for 'unless you can read byte code' – home Jan 03 '13 at 20:35
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Chuck Norris _can_ read byte code. He can sing it too! – ppeterka Jan 03 '13 at 20:36

score 0 · Answer 6 · answered Jan 03 '13 at 20:36

0

Any binary file editor will do - gHex or xxd are two recommendations.

Note, this won't really help you unless you can understand the bytecode given to you by the .class file...

answered Jan 03 '13 at 20:36

Makoto

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How do I read a Java class file (Java bytecode)

6 Answers6

Read bytecode

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