code: public void execute( EnforcerRuleHelper helper )
          throws EnforcerRuleException
      {
          String javaVersion = SystemUtils.JAVA_VERSION_TRIMMED;
          Log log = helper.getLog();
  
          log.debug( "Detected Java String: " + javaVersion );
          javaVersion = normalizeJDKVersion( javaVersion );
          log.debug( "Normalized Java String: " + javaVersion );
  
          ArtifactVersion detectedJdkVersion = new DefaultArtifactVersion( javaVersion );
  
          log.debug( "Parsed Version: Major: " + detectedJdkVersion.getMajorVersion() + " Minor: "
              + detectedJdkVersion.getMinorVersion() + " Incremental: " + detectedJdkVersion.getIncrementalVersion()
              + " Build: " + detectedJdkVersion.getBuildNumber() + " Qualifier: " + detectedJdkVersion.getQualifier() );
  
          enforceVersion( helper.getLog(), "JDK", getVersion(), detectedJdkVersion );
      }
docs: /*
  (non-Javadoc)
  
  @see org.apache.maven.enforcer.rule.api.EnforcerRule#execute(org.apache.maven.enforcer.rule.api.EnforcerRuleHelper)