Turn on many more Eclipse warnings, and fix them

- Warn on empty statements, e.g. "for (;;);". These may be
   typos and are easily replaced by "for (;;) {}" which is more
   explicit.
 - Warn on field hiding. This allows cleanup of many acceptance test
   members, at the cost of a couple of renames and the occasional
   suppression (when the field is in a public nested enum that shadows
   a public constant).
 - Warn on unnecessary casts.
 - Warn on unused declared thrown exceptions. In addition to reducing
   method signature length and number of imports, this also eliminated
   some impossible catch blocks.
 - Warn on missing @Override annotations.
 - Warn on unused parameters. This is likely the most controversial,
   as a few relatively common patterns require unused parameters in a
   way that Eclipse can't ignore. However, it also resulted in cleanup
   of a lot of unnecessary injections and method parameters, so I
   think the cost was worth it.

Change-Id: I7224be8b1c798613a127c88507e8cce400679e5d

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/AccountGroupInfoScreen.java

@@ -96,6 +96,7 @@ public class AccountGroupInfoScreen extends AccountGroupScreen {
         final String newName = groupNameTxt.getText().trim();
         GroupApi.renameGroup(getGroupUUID(), newName,
             new GerritCallback<com.google.gerrit.client.VoidResult>() {
+              @Override
               public void onSuccess(final com.google.gerrit.client.VoidResult result) {
                 saveName.setEnabled(false);
                 setPageTitle(Util.M.group(newName));
@@ -135,6 +136,7 @@ public class AccountGroupInfoScreen extends AccountGroupScreen {
           String ownerId = ownerUuid != null ? ownerUuid.get() : newOwner;
           GroupApi.setGroupOwner(getGroupUUID(), ownerId,
               new GerritCallback<GroupInfo>() {
+                @Override
                 public void onSuccess(final GroupInfo result) {
                   updateOwnerGroup(result);
                   saveOwner.setEnabled(false);
@@ -165,6 +167,7 @@ public class AccountGroupInfoScreen extends AccountGroupScreen {
         final String txt = descTxt.getText().trim();
         GroupApi.setGroupDescription(getGroupUUID(), txt,
             new GerritCallback<VoidResult>() {
+              @Override
               public void onSuccess(final VoidResult result) {
                 saveDesc.setEnabled(false);
               }
@@ -193,6 +196,7 @@ public class AccountGroupInfoScreen extends AccountGroupScreen {
       public void onClick(final ClickEvent event) {
         GroupApi.setGroupOptions(getGroupUUID(),
             visibleToAllCheckBox.getValue(), new GerritCallback<VoidResult>() {
+              @Override
               public void onSuccess(final VoidResult result) {
                 saveGroupOptions.setEnabled(false);
               }

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/AccountGroupMembersScreen.java

@@ -172,6 +172,7 @@ public class AccountGroupMembersScreen extends AccountGroupScreen {
     addMemberBox.setEnabled(false);
     GroupApi.addMember(getGroupUUID(), nameEmail,
         new GerritCallback<AccountInfo>() {
+          @Override
           public void onSuccess(final AccountInfo memberInfo) {
             addMemberBox.setEnabled(true);
             addMemberBox.setText("");
@@ -200,6 +201,7 @@ public class AccountGroupMembersScreen extends AccountGroupScreen {
     addIncludeBox.setEnabled(false);
     GroupApi.addIncludedGroup(getGroupUUID(), uuid.get(),
         new GerritCallback<GroupInfo>() {
+          @Override
           public void onSuccess(final GroupInfo result) {
             addIncludeBox.setEnabled(true);
             addIncludeBox.setText("");
@@ -248,6 +250,7 @@ public class AccountGroupMembersScreen extends AccountGroupScreen {
       if (!ids.isEmpty()) {
         GroupApi.removeMembers(getGroupUUID(), ids,
             new GerritCallback<VoidResult>() {
+              @Override
               public void onSuccess(final VoidResult result) {
                 for (int row = 1; row < table.getRowCount();) {
                   final AccountInfo i = getRowItem(row);
@@ -353,6 +356,7 @@ public class AccountGroupMembersScreen extends AccountGroupScreen {
       if (!ids.isEmpty()) {
         GroupApi.removeIncludedGroups(getGroupUUID(), ids,
             new GerritCallback<VoidResult>() {
+              @Override
               public void onSuccess(final VoidResult result) {
                 for (int row = 1; row < table.getRowCount();) {
                   final GroupInfo i = getRowItem(row);

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/CreateGroupScreen.java

@@ -128,6 +128,7 @@ public class CreateGroupScreen extends Screen {
 
     addNew.setEnabled(false);
     GroupApi.createGroup(newName, new GerritCallback<GroupInfo>() {
+      @Override
       public void onSuccess(final GroupInfo result) {
         History.newItem(Dispatcher.toGroup(result.getGroupId(),
             AccountGroupScreen.MEMBERS));

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/GroupReferenceBox.java

@@ -133,6 +133,7 @@ public class GroupReferenceBox extends Composite implements
     suggestBox.setTabIndex(index);
   }
 
+  @Override
   public void setFocus(boolean focused) {
     suggestBox.setFocus(focused);
   }

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/ProjectBranchesScreen.java

@@ -316,6 +316,7 @@ public class ProjectBranchesScreen extends ProjectScreen {
     private void deleteBranches(final Set<String> branches) {
       ProjectApi.deleteBranches(getProjectKey(), branches,
           new GerritCallback<VoidResult>() {
+            @Override
             public void onSuccess(VoidResult result) {
               for (int row = 1; row < table.getRowCount();) {
                 BranchInfo k = getRowItem(row);

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/RefPatternBox.java

@@ -27,16 +27,19 @@ import java.text.ParseException;
 
 public class RefPatternBox extends ValueBox<String> {
   private static final Renderer<String> RENDERER = new Renderer<String>() {
+    @Override
     public String render(String ref) {
       return ref;
     }
 
+    @Override
     public void render(String ref, Appendable dst) throws IOException {
       dst.append(render(ref));
     }
   };
 
   private static final Parser<String> PARSER = new Parser<String>() {
+    @Override
     public String parse(CharSequence text) throws ParseException {
       String ref = text.toString();
 

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/ValueEditor.java

@@ -86,6 +86,7 @@ public class ValueEditor<T> extends Composite implements HasEditorErrors<T>,
     editPanel.setVisible(true);
   }
 
+  @Override
   public ValueBoxEditor<T> asEditor() {
     if (editProxy == null) {
       editProxy = new EditorProxy();
@@ -133,6 +134,7 @@ public class ValueEditor<T> extends Composite implements HasEditorErrors<T>,
     startHandlers.enabled = enabled;
   }
 
+  @Override
   public void showErrors(List<EditorError> errors) {
     StringBuilder buf = new StringBuilder();
     for (EditorError error : errors) {