Some will argue that Duplication is the worst coding sin because it perpetuates all the others. For instance, copying and pasting a block of code duplicates its Bugs and Potential Bugs, its Coding Standards Breaches, and so on. It's a meta-sin, if you will.
To help you detect and eliminate duplication, SonarQube uses its own copy/paste detection engine, which can detect duplications:
Add the Duplications widget to your dashboard:
From there, you end up in the component viewer:
To display the source of a particular instance of a block, click on the file name.
By default, the scope of duplication detection is the project for standard projects and the module for multi-module projects. To detect duplications between the modules of your project and between the different projects analyzed on your SonarQube platform, log in as a a System administrator, go to Settings > General Settings > General > Duplications and set the Cross project duplication detection property to true. Then run another analysis on your projects. You also have the option of setting this at the project level: Configuration > General > Duplications.
See the following blog post: Manage Duplicated Code with Sonar.