Question: What would be the easiest way to view classes, methods, properties, etc. inside a jar file?
I'm looking for something equivalent to the very useful  *Lutz Roeder .NET Reflector*  - for Java

Answer: 
> 
> In case someone don't know this already, a JAR file is just a ZIP file
>  that contains the program's classes, resources, etc., and some
>  metadata. You can extract one to see how it's put together.
> 
> 
> 

Hence I am using `unzip` command which is easy to remember and use.

`unzip -l <jar-file-name>.jar` 

For example, if you have a jar file with name `test.jar` then `unzip -l test.jar` will list all the content of jar file.

**While all other answers are great, but in most of them, you would have to use some software like `7 zip` or `JDK` or some other eclipse tool while this doesn't require you to have any of these big s/w and it comes by default in linux and mac so its very lightweight and handy to use**. 

You can also use `zipinfo <your jar file>`. if your OS supports this.
Eclipse 3.4 JDT

It is not the quickest way because you have to drag it into your eclipse first.
But you will have full java class browsing, even with decompile enabled.