How to install rpm file on Ubuntu?

A file with extension .rpm is generated by RPM Package Manager or Redhat Package Manager.
How to install this kind of file on your Ubuntu? It need alien's help.

NAME
       alien - Convert or install an alien binary package

SYNOPSIS
        alien [--to-deb] [--to-rpm] [--to-tgz] [--to-slp] [options] file [...]

DESCRIPTION
       alien is a program that converts between Red Hat rpm, Debian deb, Stampede slp, Slackware
       tgz, and Solaris pkg file formats. If you want to use a package from another linux
       distribution than the one you have installed on your system, you can use alien to convert
       it to your preferred package format and install it. It also supports LSB packages.

First check if alien has been installed on your Ubuntu. It need dpkg command (dpkg - package manager for Debian) or Ubuntu Software Center.

I installed once. Have you installed? If not please run

~$sudo apt-get install alien

Now I can start installing my rpm file. For example, sqldeveloper-4.0.0.13.80-1.noarch.rpm

~$sudo alien sqldeveloper-4.0.0.13.80-1.noarch.rpm

It will generate a sqldeveloper_4.0.0.13.80-2_all.deb file. Now you can use command line

~$sudo dpkg -i sqldeveloper_4.0.0.13.80-2_all.deb

or right click it to open with Ubuntu Software Center.