IntelliJ IDEA Tips & Tricks #8: Automatically Decompile the .class File by Viewing It!
Often, you may need to decompile a Java class file. There are many reasons for that:
the corresponding source code for an API may not be available and you want to see how the implementation looks like
you want to see what the compiler has done with the code (e.g., how a try-with-resources got translated by the compiler)
debug the code because the code seem to be fine by the compiler seem to think / process the code differently.
In these scenarios, it's easy to "decompile" a ".class" file - just open it in the editor and you'll see the decompiled source code. Note that it is a read-only file - you can modify the source code directly and try recompiling it and run it.