Missing Javadoc comments
The use of magic numbers
Naming conventions of variables and methods
Method's argument length and line lengths
The use of imports
The spaces between some characters
The good practices of class construction
The Checkstyle plugin can be downloaded from http://sourceforge.net/projects/eclipse-cs/, or you can install it through Eclipse Marketplace. Just search for Checkstyle.
Click on the Install New Software menu; Eclipse will open a new wizard.
Click on the Add button and a new Add Repository pop up will appear.
Click on the Archive... button and browse to the downloaded ZIP file's location.
Select defaults, finish installation, and restart Eclipse.
The following screenshot shows the Checkstyle components to be installed...