How to solve "Failed to execute goal org.apache.maven.plugins:maven-clean-plugin:2.4.1:clean (default-clean) on project"?

I am beginner in maven.when i click "clean & Build" to rebuild my project in netbeans.then "Failed to execute goal org.apache.maven.plugins:maven-clean-plugin:2.4.1:clean (default-clean) on project xxxx-web: Failed to clean project: Failed to delete D:\Gps2.x\xxxx-web\target\xxxx-web-2.11-SNAPSHOT\WEB-INF\lib\validation-api-1.0.0.GA.jar -> [Help 1]

To see the full stack trace of the errors, re-run Maven with the -e switch. Re-run Maven using the -X switch to enable full debug logging."

Or how to build a war file using maven package?