Decrease visibility of inner classes. #1555

Possibility to instantiate private checks was added.

Fixes `PublicInnerClass` inspection violation.

Description:
>Reports public inner classes.

src/main/java/com/puppycrawl/tools/checkstyle/PackageObjectFactory.java

@@ -19,6 +19,7 @@
 
 package com.puppycrawl.tools.checkstyle;
 
+import java.lang.reflect.Constructor;
 import java.util.Set;
 
 import org.apache.commons.logging.Log;
@@ -112,7 +113,9 @@ class PackageObjectFactory implements ModuleFactory {
         throws CheckstyleException {
         try {
             final Class<?> clazz = Class.forName(className, true, moduleClassLoader);
-            return clazz.getDeclaredConstructor().newInstance();
+            final Constructor<?> declaredConstructor = clazz.getDeclaredConstructor();
+            declaredConstructor.setAccessible(true);
+            return declaredConstructor.newInstance();
         }
         catch (final ReflectiveOperationException exception) {
             throw new CheckstyleException("Unable to find class for " + className, exception);

src/main/java/com/puppycrawl/tools/checkstyle/gui/FileDrop.java

@@ -228,7 +228,7 @@ class FileDrop {
      *
      * @since 1.0
      */
-    public interface Listener {
+    interface Listener {
         /**
          * This method is called when files have been successfully dropped.
          *

src/main/java/com/puppycrawl/tools/checkstyle/gui/JTreeTable.java

@@ -279,7 +279,7 @@ public class JTreeTable extends JTable {
      * TreeTableCellEditor implementation. Component returned is the
      * JTree.
      */
-    public class TreeTableCellEditor extends AbstractCellEditor implements
+    private class TreeTableCellEditor extends AbstractCellEditor implements
             TableCellEditor {
         @Override
         public Component getTableCellEditorComponent(JTable table,

src/test/java/com/puppycrawl/tools/checkstyle/TreeWalkerTest.java

@@ -294,7 +294,7 @@ public class TreeWalkerTest extends BaseCheckTestSupport {
         treeWalker.processFiltered(file, lines);
     }
 
-    public static class BadJavaDocCheck extends Check {
+    private static class BadJavaDocCheck extends Check {
         @Override
         public int[] getDefaultTokens() {
             return getAcceptableTokens();

src/test/java/com/puppycrawl/tools/checkstyle/api/AutomaticBeanTest.java

@@ -98,7 +98,7 @@ public class AutomaticBeanTest {
     }
 
     @SuppressWarnings("unused")
-    public static class TestBean extends AutomaticBean {
+    private static class TestBean extends AutomaticBean {
 
         private String privateField;
 

src/test/java/com/puppycrawl/tools/checkstyle/checks/FileSetCheckLifecycleTest.java

@@ -93,7 +93,7 @@ public class FileSetCheckLifecycleTest
                 TestFileSetCheck.isFileContentAvailable());
     }
 
-    public static class TestFileSetCheck extends AbstractFileSetCheck {
+    private static class TestFileSetCheck extends AbstractFileSetCheck {
         private static boolean destroyed;
         private static boolean fileContentAvailable;
 

src/test/java/com/puppycrawl/tools/checkstyle/checks/javadoc/AbstractJavadocCheckTest.java

@@ -81,7 +81,7 @@ public class AbstractJavadocCheckTest extends BaseCheckTestSupport {
         verify(checker, getPath("javadoc/InputCorrectJavaDocParagraphCheck.java"), expected);
     }
 
-    public static class TempCheck extends AbstractJavadocCheck {
+    private static class TempCheck extends AbstractJavadocCheck {
 
         @Override
         public int[] getDefaultJavadocTokens() {

src/test/java/com/puppycrawl/tools/checkstyle/checks/javadoc/JavadocParseTreeTest.java

@@ -271,7 +271,7 @@ public class JavadocParseTreeTest {
         Assert.assertEquals(t1.toStringTree(parser), t2.toStringTree(parser));
     }
 
-    public static class FailOnErrorListener extends BaseErrorListener {
+    private static class FailOnErrorListener extends BaseErrorListener {
         @Override
         public void syntaxError(
                 Recognizer<?, ?> aRecognizer, Object aOffendingSymbol,

src/test/java/com/puppycrawl/tools/checkstyle/comments/AllBlockCommentsTest.java

@@ -47,7 +47,7 @@ public class AllBlockCommentsTest extends BaseCheckTestSupport {
         Assert.assertTrue(ALL_COMMENTS.isEmpty());
     }
 
-    public static class BlockCommentListenerCheck extends Check {
+    private static class BlockCommentListenerCheck extends Check {
         @Override
         public boolean isCommentNodesRequired() {
             return true;

src/test/java/com/puppycrawl/tools/checkstyle/comments/AllSinglelineCommentsTest.java

@@ -46,7 +46,7 @@ public class AllSinglelineCommentsTest extends BaseCheckTestSupport {
         Assert.assertTrue(ALL_COMMENTS.isEmpty());
     }
 
-    public static class SinglelineCommentListenerCheck extends Check {
+    private static class SinglelineCommentListenerCheck extends Check {
         @Override
         public boolean isCommentNodesRequired() {
             return true;