[MASSEMBLY-876] - Upgrade parent to 31
 o Fixed some checkstyle issues according to the upgrade
   of checkstyle plugin.
 o Cleaned pom.
diff --git a/pom.xml b/pom.xml
index 5b1b57f..b453154 100644
--- a/pom.xml
+++ b/pom.xml
@@ -25,7 +25,7 @@
   <parent>
     <artifactId>maven-plugins</artifactId>
     <groupId>org.apache.maven.plugins</groupId>
-    <version>30</version>
+    <version>31</version>
     <relativePath>../../pom/maven/maven-plugins/pom.xml</relativePath>
   </parent>
 
@@ -373,8 +373,6 @@
       </pluginRepositories>
 
       <properties>
-        <!-- See https://issues.apache.org/jira/browse/MINVOKER-213 -->
-        <invokerPluginVersion>3.0.0</invokerPluginVersion>
         <test.remote.repo.url>file://${project.build.testOutputDirectory}/remote-repository</test.remote.repo.url>
         <it.streamLogs>false</it.streamLogs>
         <testVersion>${project.version}</testVersion>
@@ -386,7 +384,6 @@
           <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-invoker-plugin</artifactId>
-            <version>${invokerPluginVersion}</version>
             <configuration>
               <properties>
                 <useJvmChmod>${useJvmChmod}</useJvmChmod>
diff --git a/src/main/java/org/apache/maven/plugins/assembly/archive/archiver/PrefixedArchivedFileSet.java b/src/main/java/org/apache/maven/plugins/assembly/archive/archiver/PrefixedArchivedFileSet.java
index 6c1e77e..73bfb73 100644
--- a/src/main/java/org/apache/maven/plugins/assembly/archive/archiver/PrefixedArchivedFileSet.java
+++ b/src/main/java/org/apache/maven/plugins/assembly/archive/archiver/PrefixedArchivedFileSet.java
@@ -43,7 +43,7 @@
      * @param rootPrefix The root prefix.
      * @param selectors  The file selectors.
      */
-    public PrefixedArchivedFileSet( ArchivedFileSet fileSet, String rootPrefix, FileSelector[] selectors )
+    PrefixedArchivedFileSet( ArchivedFileSet fileSet, String rootPrefix, FileSelector[] selectors )
     {
         this.fileSet = fileSet;
         this.selectors = selectors;
diff --git a/src/main/java/org/apache/maven/plugins/assembly/archive/archiver/PrefixedFileSet.java b/src/main/java/org/apache/maven/plugins/assembly/archive/archiver/PrefixedFileSet.java
index 2a9eda3..1ceead1 100644
--- a/src/main/java/org/apache/maven/plugins/assembly/archive/archiver/PrefixedFileSet.java
+++ b/src/main/java/org/apache/maven/plugins/assembly/archive/archiver/PrefixedFileSet.java
@@ -43,7 +43,7 @@
      * @param rootPrefix The root prefix
      * @param selectors  The file selectors.
      */
-    public PrefixedFileSet( final FileSet fileSet, final String rootPrefix, final FileSelector[] selectors )
+    PrefixedFileSet( final FileSet fileSet, final String rootPrefix, final FileSelector[] selectors )
     {
         this.fileSet = fileSet;
         this.selectors = selectors;
diff --git a/src/main/java/org/apache/maven/plugins/assembly/archive/phase/wrappers/GroupVersionAlignmentWrapper.java b/src/main/java/org/apache/maven/plugins/assembly/archive/phase/wrappers/GroupVersionAlignmentWrapper.java
index d981909..3fa28a9 100644
--- a/src/main/java/org/apache/maven/plugins/assembly/archive/phase/wrappers/GroupVersionAlignmentWrapper.java
+++ b/src/main/java/org/apache/maven/plugins/assembly/archive/phase/wrappers/GroupVersionAlignmentWrapper.java
@@ -35,7 +35,7 @@
     /**
      * @param alignment @{link {@link GroupVersionAlignment}
      */
-    public GroupVersionAlignmentWrapper( final GroupVersionAlignment alignment )
+    GroupVersionAlignmentWrapper( final GroupVersionAlignment alignment )
     {
         this.alignment = alignment;
     }
diff --git a/src/main/java/org/apache/maven/plugins/assembly/interpolation/AssemblyInterpolator.java b/src/main/java/org/apache/maven/plugins/assembly/interpolation/AssemblyInterpolator.java
index 307b9f5..fe55eaa 100644
--- a/src/main/java/org/apache/maven/plugins/assembly/interpolation/AssemblyInterpolator.java
+++ b/src/main/java/org/apache/maven/plugins/assembly/interpolation/AssemblyInterpolator.java
@@ -158,7 +158,7 @@
 
         private final File basedir;
 
-        public PathTranslatingPostProcessor( final File basedir )
+        PathTranslatingPostProcessor( final File basedir )
         {
             this.basedir = basedir;
         }
diff --git a/src/main/java/org/apache/maven/plugins/assembly/io/PrefixedClasspathLocatorStrategy.java b/src/main/java/org/apache/maven/plugins/assembly/io/PrefixedClasspathLocatorStrategy.java
index 9875ba8..96be53e 100644
--- a/src/main/java/org/apache/maven/plugins/assembly/io/PrefixedClasspathLocatorStrategy.java
+++ b/src/main/java/org/apache/maven/plugins/assembly/io/PrefixedClasspathLocatorStrategy.java
@@ -32,7 +32,7 @@
 
     private final String prefix;
 
-    public PrefixedClasspathLocatorStrategy( String prefix )
+    PrefixedClasspathLocatorStrategy( String prefix )
     {
         this.prefix = formatPrefix( prefix );
     }
diff --git a/src/main/java/org/apache/maven/plugins/assembly/io/RelativeFileLocatorStrategy.java b/src/main/java/org/apache/maven/plugins/assembly/io/RelativeFileLocatorStrategy.java
index be8a936..42cc39a 100644
--- a/src/main/java/org/apache/maven/plugins/assembly/io/RelativeFileLocatorStrategy.java
+++ b/src/main/java/org/apache/maven/plugins/assembly/io/RelativeFileLocatorStrategy.java
@@ -35,7 +35,7 @@
 
     private final File basedir;
 
-    public RelativeFileLocatorStrategy( File basedir )
+    RelativeFileLocatorStrategy( File basedir )
     {
         this.basedir = basedir;
     }
diff --git a/src/main/java/org/apache/maven/plugins/assembly/utils/LineEndings.java b/src/main/java/org/apache/maven/plugins/assembly/utils/LineEndings.java
index 7a15115..d2b18ff 100644
--- a/src/main/java/org/apache/maven/plugins/assembly/utils/LineEndings.java
+++ b/src/main/java/org/apache/maven/plugins/assembly/utils/LineEndings.java
@@ -35,7 +35,7 @@
 
     private final String lineEndingCharacters;
 
-    private LineEndings( String lineEndingCharacters )
+    LineEndings( String lineEndingCharacters )
     {
         this.lineEndingCharacters = lineEndingCharacters;
     }
diff --git a/src/main/java/org/apache/maven/plugins/assembly/utils/LinuxLineFeedInputStream.java b/src/main/java/org/apache/maven/plugins/assembly/utils/LinuxLineFeedInputStream.java
index c1b2449..9b51026 100644
--- a/src/main/java/org/apache/maven/plugins/assembly/utils/LinuxLineFeedInputStream.java
+++ b/src/main/java/org/apache/maven/plugins/assembly/utils/LinuxLineFeedInputStream.java
@@ -39,7 +39,7 @@
 
     private boolean eofSeen = false;
 
-    public LinuxLineFeedInputStream( InputStream in, boolean ensureLineFeedAtEndOfFile )
+    LinuxLineFeedInputStream( InputStream in, boolean ensureLineFeedAtEndOfFile )
     {
         this.target = in;
         this.ensureLineFeedAtEndOfFile = ensureLineFeedAtEndOfFile;
diff --git a/src/main/java/org/apache/maven/plugins/assembly/utils/WindowsLineFeedInputStream.java b/src/main/java/org/apache/maven/plugins/assembly/utils/WindowsLineFeedInputStream.java
index 0ff2f78..3cd15ca 100644
--- a/src/main/java/org/apache/maven/plugins/assembly/utils/WindowsLineFeedInputStream.java
+++ b/src/main/java/org/apache/maven/plugins/assembly/utils/WindowsLineFeedInputStream.java
@@ -41,7 +41,7 @@
 
     private boolean eofSeen = false;
 
-    public WindowsLineFeedInputStream( InputStream in, boolean ensureLineFeedAtEndOfFile )
+    WindowsLineFeedInputStream( InputStream in, boolean ensureLineFeedAtEndOfFile )
     {
         this.target = in;
         this.ensureLineFeedAtEndOfFile = ensureLineFeedAtEndOfFile;