class file in the editor in IntelliJ IDEA and then select View | Show Bytecode from the main menu. Of course, you can always open the bytecode viewer for any compiled class. This means you can use breakpoints anywhere in the decompiled code with almost the same experience that you’d normally have when you debug your source code. The decompiler can not only convert bytecode to Java code, but it can also debug it. The yellow notification panel above the editor informs you that you’re reading a decompiled file. However, if you open the same file in IntelliJ IDEA, the IDE shows you the human-readable Java code from your. class file in a text editor, you’ll only see the bytecode that sometimes makes little sense. How do you look inside and make sure it actually has what you need? You just downloaded it from the Internet and don’t have the source code for it. Let’s say you have a library packed in a. The Java bytecode decompiler in IntelliJ IDEA is a built-in tool that allows you to read compiled bytecode as if it were human-readable Java code. One of these features is the Java bytecode decompiler. In IntelliJ IDEA, there are several features that many people don’t even notice, even as they use them all the time. If you know of a good CLI decompiler, I'd be very interested to hear of it (there is JAD, but AFAIK that only supports Java < 1.5).When something is there for us day after day, we tend to take it for granted. Note however that JD-GUI has no CLI interface. Using it goes something like this: jd-gui myjar.jar Sudo chown root:root /usr/local/bin/jd-gui This is no great loss though you can get it to dump all the sources to disk with Ctrl+Alt+S for perusal with grep/vim/Eclipse etc. Frustratingly, its multi-file search functionality never works for me (note that Ctrl+F search-on-the-page is fine). I tend to use JD-GUI, because it's quick and does what I need it to. There aren't many good java decompilers to choose from. To make sense of it, you need to decompile it into something readable. Here are the read commands:Įxtract specific file, creating dirs as requiredĮxtracting the bytecode itself isn't usually terribly useful though. Personally I use jar because it feels more natural, and allows for other operations such as updating contents too.

See inside jar file