Remove explicit initialization of default values

Default values are false for boolean, 0 for int and char, and null
for object references.

Explicitly initializing a variable to the default value causes it
to be initialized twice.

Enable the Checkstyle warning, and fix occurences of it.

Change-Id: I1971e438fc506c18458b1402fcb01e43fa61ff8c

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/BinaryResult.java

@@ -62,7 +62,7 @@ public abstract class BinaryResult implements Closeable {
   private Charset characterEncoding;
   private long contentLength = -1;
   private boolean gzip = true;
-  private boolean base64 = false;
+  private boolean base64;
   private String attachmentName;
 
   /** @return the MIME type of the result, for HTTP clients. */

gerrit-gwtui/src/main/java/com/google/gerrit/client/documentation/DocTable.java

@@ -28,8 +28,8 @@ import com.google.gwt.user.client.ui.HTMLTable.CellFormatter;
 class DocTable extends NavigationTable<DocInfo> {
   private static final int C_TITLE = 1;
 
-  private int rows = 0;
-  private int dataBeginRow = 0;
+  private int rows;
+  private int dataBeginRow;
 
   DocTable() {
     super(Util.C.docItemHelp());

gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CommentedActionDialog.java

@@ -35,7 +35,7 @@ public abstract class CommentedActionDialog extends AutoCenterDialogBox
   protected final FlowPanel contentPanel;
   protected FocusWidget focusOn;
 
-  protected boolean sent = false;
+  protected boolean sent;
 
   public CommentedActionDialog(final String title, final String heading) {
     super(/* auto hide */false, /* modal */true);

gerrit-pgm/src/main/java/com/google/gerrit/pgm/Init.java

@@ -52,7 +52,7 @@ public class Init extends BaseInit {
   private boolean noAutoStart;
 
   @Option(name = "--skip-plugins", usage = "Don't install plugins")
-  private boolean skipPlugins = false;
+  private boolean skipPlugins;
 
   @Option(name = "--list-plugins", usage = "List available plugins")
   private boolean listPlugins;

gerrit-server/src/main/java/com/google/gerrit/server/project/RefControl.java

@@ -473,8 +473,8 @@ public class RefControl {
   }
 
   private static class AllowedRange {
-    private int allowMin = 0;
-    private int allowMax = 0;
+    private int allowMin;
+    private int allowMax;
     private int blockMin = Integer.MIN_VALUE;
     private int blockMax = Integer.MAX_VALUE;
 

gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/AdminSetParent.java

@@ -81,7 +81,7 @@ final class AdminSetParent extends SshCommand {
   @Inject
   private Provider<ListChildProjects> listChildProjects;
 
-  private Project.NameKey newParentKey = null;
+  private Project.NameKey newParentKey;
 
   @Override
   protected void run() throws Failure {

plugins/cookbook-plugin

@@ -1 +1 @@
-Subproject commit 32b238a2ff9625b17d9dc44e145de269ec833736
+Subproject commit 9286b87ba7936af7f66b6562adb54e8d276cb5cb

tools/checkstyle.xml

@@ -95,6 +95,7 @@ edited to remove noisy warnings.
     </module>
     <module name="RedundantImport"/>
     <module name="RedundantModifier"/>
+    <module name="ExplicitInitialization"/>
   </module>
   <module name="FileTabCharacter">
     <property name="severity" value="ignore"/>