Prefer JDK built-in methods for string joining

Author: elharo

src/main/java/org/apache/maven/plugins/pmd/AbstractPmdReport.java

@@ -41,7 +41,6 @@
 import org.apache.maven.reporting.AbstractMavenReport;
 import org.apache.maven.reporting.MavenReportException;
 import org.codehaus.plexus.util.FileUtils;
-import org.codehaus.plexus.util.StringUtils;
 
 /**
  * Base class for the PMD reports.
@@ -390,7 +389,7 @@ private boolean isDirectoryExcluded(Collection<File> excludedRootFiles, File sou
     /**
      * Gets the comma separated list of effective include patterns.
      *
-     * @return The comma separated list of effective include patterns, never <code>null</code>.
+     * @return the comma separated list of effective include patterns, never <code>null</code>.
      */
     private String getIncludes() {
         Collection<String> patterns = new LinkedHashSet<>();
@@ -400,20 +399,20 @@ private String getIncludes() {
         if (patterns.isEmpty()) {
             patterns.add("**/*.java");
         }
-        return StringUtils.join(patterns.iterator(), ",");
+        return String.join(",", patterns);
     }
 
     /**
      * Gets the comma separated list of effective exclude patterns.
      *
-     * @return The comma separated list of effective exclude patterns, never <code>null</code>.
+     * @return the comma separated list of effective exclude patterns, never <code>null</code>.
      */
     private String getExcludes() {
         Collection<String> patterns = new LinkedHashSet<>(FileUtils.getDefaultExcludesAsList());
         if (excludes != null) {
             patterns.addAll(excludes);
         }
-        return StringUtils.join(patterns.iterator(), ",");
+        return String.join(",", patterns);
     }
 
     protected boolean isXml() {

src/main/java/org/apache/maven/plugins/pmd/PmdReport.java

@@ -43,7 +43,6 @@
 import org.codehaus.plexus.resource.loader.FileResourceCreationException;
 import org.codehaus.plexus.resource.loader.FileResourceLoader;
 import org.codehaus.plexus.resource.loader.ResourceNotFoundException;
-import org.codehaus.plexus.util.StringUtils;
 
 /**
  * Creates a PMD site report based on the rulesets and configuration set in the plugin.
@@ -492,7 +491,7 @@ private String determineAuxClasspath() throws MavenReportException {
 
                 getLog().debug("Using aux classpath: " + classpath);
             }
-            return StringUtils.join(classpath.iterator(), File.pathSeparator);
+            return String.join(File.pathSeparator, classpath);
         } catch (Exception e) {
             throw new MavenReportException(e.getMessage(), e);
         }