I am trying to generate a simple smart contract wrapper using solc and web3j in ubuntu.

I have downloaded the source as defined in <https://docs.web3j.io/command_line.html> 

Release package can be obtained from <https://github.com/web3j/web3j/releases/tag/v4.1.0>. 

I have download the source from <https://github.com/web3j/web3j/archive/v4.1.0.zip>

After unwrapping the zip package I can't find any bin directory as the document page shows 

```
unzip web3j-<version>.zip
creating: web3j-3.0.0/lib/
inflating: web3j-3.0.0/lib/core-1.0.2-all.jarcreating: web3j-3.0.0/bin/
inflating: web3j-3.0.0/bin/web3j
inflating: web3j-3.0.0/bin/web3j.bat

```

How to get the bin directory?