Avoid Collections#sort

With the introduction of default methods in Java 8, Java finally grew a
List#sort method that can be used in place of the static
Collections#sort. Convert simple in-place sorts that need to be in-place
sorts to use this method where possible.

During the course of this change, it became obvious that many instances
of sort were just sorting a newly-created ArrayList in place. These can
be replaced with more idiomatic Stream constructions, sometimes even
eliminating a loop to populate the list.

One difference between List#sort and Collections#sort is there is no
List#sort() with no arguments; callers must always pass either
naturalOrder() or a null comparators. In this change, there were so few
remaining instances of sorting by natural order that typing
naturalOrder() didn't seem too repetitious, and it is quite readable.

Change-Id: I4d89421a72127e9a36cbd32aeac425c0471a1b3f

gerrit-gwtui-common/src/main/java/com/google/gerrit/client/info/ChangeInfo.java

@@ -32,7 +32,6 @@ import com.google.gwt.core.client.JsArrayString;
 import com.google.gwtjsonrpc.client.impl.ser.JavaSqlTimestamp_JsonSerializer;
 import java.sql.Timestamp;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -448,9 +447,8 @@ public class ChangeInfo extends JavaScriptObject {
 
     public static void sortRevisionInfoByNumber(JsArray<RevisionInfo> list) {
       final int editParent = findEditParent(list);
-      Collections.sort(
+      Natives.asList(list)
-          Natives.asList(list),
+          .sort(comparing(r -> !r.isEdit() ? 2 * (r._number() - 1) + 1 : 2 * editParent));
-          comparing(r -> !r.isEdit() ? 2 * (r._number() - 1) + 1 : 2 * editParent));
     }
 
     public static int findEditParent(JsArray<RevisionInfo> list) {

gerrit-gwtui-common/src/main/java/com/google/gerrit/client/info/FileInfo.java

@@ -19,7 +19,6 @@ import com.google.gerrit.common.data.FilenameComparator;
 import com.google.gerrit.reviewdb.client.Patch;
 import com.google.gwt.core.client.JavaScriptObject;
 import com.google.gwt.core.client.JsArray;
-import java.util.Collections;
 import java.util.Comparator;
 
 public class FileInfo extends JavaScriptObject {
@@ -55,8 +54,7 @@ public class FileInfo extends JavaScriptObject {
   public final native void _row(int r) /*-{ this._row = r }-*/;
 
   public static void sortFileInfoByPath(JsArray<FileInfo> list) {
-    Collections.sort(
+    Natives.asList(list).sort(Comparator.comparing(FileInfo::path, FilenameComparator.INSTANCE));
-        Natives.asList(list), Comparator.comparing(FileInfo::path, FilenameComparator.INSTANCE));
   }
 
   public static String getFileName(String path) {

gerrit-gwtui-common/src/main/java/com/google/gerrit/client/rpc/NativeMap.java

@@ -14,11 +14,12 @@
 
 package com.google.gerrit.client.rpc;
 
+import static java.util.stream.Collectors.toCollection;
+
 import com.google.gwt.core.client.JavaScriptObject;
 import com.google.gwt.core.client.JsArray;
 import com.google.gwt.user.client.rpc.AsyncCallback;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
@@ -57,10 +58,7 @@ public class NativeMap<T extends JavaScriptObject> extends JavaScriptObject {
   }
 
   public final List<String> sortedKeys() {
-    Set<String> keys = keySet();
+    return keySet().stream().sorted().collect(toCollection(ArrayList::new));
-    List<String> sorted = new ArrayList<>(keys);
-    Collections.sort(sorted);
-    return sorted;
   }
 
   public final native JsArray<T> values() /*-{

gerrit-gwtui/src/main/java/com/google/gerrit/client/account/MyGpgKeysScreen.java

@@ -42,7 +42,6 @@ import com.google.gwt.user.client.ui.VerticalPanel;
 import com.google.gwtexpui.clippy.client.CopyableLabel;
 import com.google.gwtexpui.globalkey.client.NpTextArea;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 
 public class MyGpgKeysScreen extends SettingsScreen {
@@ -119,7 +118,7 @@ public class MyGpgKeysScreen extends SettingsScreen {
                     List<GpgKeyInfo> list = Natives.asList(result.values());
                     // TODO(dborowitz): Sort on something more meaningful, like
                     // created date?
-                    Collections.sort(list, comparing(GpgKeyInfo::id));
+                    list.sort(comparing(GpgKeyInfo::id));
                     keys.clear();
                     keyText.setText("");
                     errorPanel.setVisible(false);

gerrit-gwtui/src/main/java/com/google/gerrit/client/account/MyIdentitiesScreen.java

@@ -14,6 +14,8 @@
 
 package com.google.gerrit.client.account;
 
+import static java.util.Comparator.naturalOrder;
+
 import com.google.gerrit.client.Gerrit;
 import com.google.gerrit.client.VoidResult;
 import com.google.gerrit.client.rpc.GerritCallback;
@@ -29,7 +31,6 @@ import com.google.gwt.user.client.Window.Location;
 import com.google.gwt.user.client.ui.Button;
 import com.google.gwt.user.client.ui.CheckBox;
 import com.google.gwt.user.client.ui.FlexTable.FlexCellFormatter;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 
@@ -169,7 +170,7 @@ public class MyIdentitiesScreen extends SettingsScreen {
 
     void display(JsArray<ExternalIdInfo> results) {
       List<ExternalIdInfo> idList = Natives.asList(results);
-      Collections.sort(idList);
+      idList.sort(naturalOrder());
 
       while (1 < table.getRowCount()) {
         table.removeRow(table.getRowCount() - 1);

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

@@ -14,6 +14,8 @@
 
 package com.google.gerrit.client.admin;
 
+import static java.util.stream.Collectors.toCollection;
+
 import com.google.gerrit.client.Gerrit;
 import com.google.gerrit.common.data.AccessSection;
 import com.google.gerrit.common.data.LabelType;
@@ -45,7 +47,6 @@ import com.google.gwt.user.client.ui.FlowPanel;
 import com.google.gwt.user.client.ui.HTMLPanel;
 import com.google.gwt.user.client.ui.ValueListBox;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 
 public class AccessSectionEditor extends Composite
@@ -205,9 +206,8 @@ public class AccessSectionEditor extends Composite
   }
 
   private void sortPermissions(AccessSection accessSection) {
-    List<Permission> permissionList = new ArrayList<>(accessSection.getPermissions());
+    accessSection.setPermissions(
-    Collections.sort(permissionList);
+        accessSection.getPermissions().stream().sorted().collect(toCollection(ArrayList::new)));
-    accessSection.setPermissions(permissionList);
   }
 
   void setEditing(boolean editing) {

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

@@ -34,7 +34,6 @@ import com.google.gwt.user.client.ui.Anchor;
 import com.google.gwt.user.client.ui.FlexTable.FlexCellFormatter;
 import com.google.gwt.user.client.ui.HTMLTable.Cell;
 import com.google.gwt.user.client.ui.Image;
-import java.util.Collections;
 import java.util.List;
 
 public class GroupTable extends NavigationTable<GroupInfo> {
@@ -106,7 +105,7 @@ public class GroupTable extends NavigationTable<GroupInfo> {
       table.removeRow(table.getRowCount() - 1);
     }
 
-    Collections.sort(list, comparing(GroupInfo::name));
+    list.sort(comparing(GroupInfo::name));
     for (GroupInfo group : list.subList(fromIndex, toIndex)) {
       final int row = table.getRowCount();
       table.insertRow(row);

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Labels.java

@@ -14,6 +14,10 @@
 
 package com.google.gerrit.client.change;
 
+import static java.util.stream.Collectors.collectingAndThen;
+import static java.util.stream.Collectors.toCollection;
+import static java.util.stream.Collectors.toList;
+
 import com.google.gerrit.client.Gerrit;
 import com.google.gerrit.client.changes.ChangeApi;
 import com.google.gerrit.client.changes.Util;
@@ -135,9 +139,12 @@ class Labels extends Grid {
   }
 
   void set(ChangeInfo info) {
-    List<String> names = new ArrayList<>(info.labels());
+    List<String> names =
+        info.labels()
+            .stream()
+            .sorted()
+            .collect(collectingAndThen(toList(), Collections::unmodifiableList));
     Set<Integer> removable = info.removableReviewerIds();
-    Collections.sort(names);
 
     resize(names.size(), 2);
 
@@ -197,8 +204,7 @@ class Labels extends Grid {
   }
 
   private static List<Integer> sort(Set<Integer> keySet, int a, int b) {
-    List<Integer> r = new ArrayList<>(keySet);
+    List<Integer> r = keySet.stream().sorted().collect(toCollection(ArrayList::new));
-    Collections.sort(r);
     if (keySet.contains(a)) {
       r.remove(Integer.valueOf(a));
       r.add(0, a);
@@ -238,31 +244,32 @@ class Labels extends Grid {
       Set<Integer> removable,
       String label,
       Map<Integer, VotableInfo> votable) {
-    List<AccountInfo> users = new ArrayList<>(in);
+    List<AccountInfo> users =
-    Collections.sort(
+        in.stream()
-        users,
+            .sorted(
-        new Comparator<AccountInfo>() {
+                new Comparator<AccountInfo>() {
-          @Override
+                  @Override
-          public int compare(AccountInfo a, AccountInfo b) {
+                  public int compare(AccountInfo a, AccountInfo b) {
-            String as = name(a);
+                    String as = name(a);
-            String bs = name(b);
+                    String bs = name(b);
-            if (as.isEmpty()) {
+                    if (as.isEmpty()) {
-              return 1;
+                      return 1;
-            } else if (bs.isEmpty()) {
+                    } else if (bs.isEmpty()) {
-              return -1;
+                      return -1;
-            }
+                    }
-            return as.compareTo(bs);
+                    return as.compareTo(bs);
-          }
+                  }
 
-          private String name(AccountInfo a) {
+                  private String name(AccountInfo a) {
-            if (a.name() != null) {
+                    if (a.name() != null) {
-              return a.name();
+                      return a.name();
-            } else if (a.email() != null) {
+                    } else if (a.email() != null) {
-              return a.email();
+                      return a.email();
-            }
+                    }
-            return "";
+                    return "";
-          }
+                  }
-        });
+                })
+            .collect(collectingAndThen(toList(), Collections::unmodifiableList));
 
     SafeHtmlBuilder html = new SafeHtmlBuilder();
     Iterator<? extends AccountInfo> itr = users.iterator();

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ReplyBox.java

@@ -16,6 +16,8 @@ package com.google.gerrit.client.change;
 
 import static com.google.gwt.event.dom.client.KeyCodes.KEY_ENTER;
 import static com.google.gwt.event.dom.client.KeyCodes.KEY_MAC_ENTER;
+import static java.util.stream.Collectors.collectingAndThen;
+import static java.util.stream.Collectors.toList;
 
 import com.google.gerrit.client.Gerrit;
 import com.google.gerrit.client.changes.ChangeApi;
@@ -123,11 +125,15 @@ public class ReplyBox extends Composite {
     this.lc = new LocalComments(project, psId.getParentKey());
     initWidget(uiBinder.createAndBindUi(this));
 
-    List<String> names = new ArrayList<>(permitted.keySet());
+    List<String> names =
+        permitted
+            .keySet()
+            .stream()
+            .sorted()
+            .collect(collectingAndThen(toList(), Collections::unmodifiableList));
     if (names.isEmpty()) {
       UIObject.setVisible(labelsParent, false);
     } else {
-      Collections.sort(names);
       renderLabels(names, all, permitted);
     }
 
@@ -439,8 +445,11 @@ public class ReplyBox extends Composite {
               clp, project, psId, Util.C.commitMessage(), copyPath(Patch.MERGE_LIST, l)));
     }
 
-    List<String> paths = new ArrayList<>(m.keySet());
+    List<String> paths =
-    Collections.sort(paths);
+        m.keySet()
+            .stream()
+            .sorted()
+            .collect(collectingAndThen(toList(), Collections::unmodifiableList));
 
     for (String path : paths) {
       if (!Patch.isMagic(path)) {

gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/AccountDashboardScreen.java

@@ -178,7 +178,7 @@ public class AccountDashboardScreen extends Screen implements ChangeListScreen {
       }
     }
 
-    Collections.sort(Natives.asList(out), outComparator());
+    Natives.asList(out).sort(outComparator());
 
     table.updateColumnsForLabels(wip, out, in, done);
     workInProgress.display(wip);

gerrit-gwtui/src/main/java/com/google/gerrit/client/dashboards/DashboardsTable.java

@@ -27,7 +27,6 @@ import com.google.gwt.user.client.ui.Anchor;
 import com.google.gwt.user.client.ui.FlexTable.FlexCellFormatter;
 import com.google.gwt.user.client.ui.Image;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -76,7 +75,7 @@ public class DashboardsTable extends NavigationTable<DashboardInfo> {
       table.removeRow(table.getRowCount() - 1);
     }
 
-    Collections.sort(list, comparing(DashboardInfo::id));
+    list.sort(comparing(DashboardInfo::id));
 
     String ref = null;
     for (DashboardInfo d : list) {

gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/CommentsCollections.java

@@ -29,7 +29,6 @@ import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gwt.core.client.JsArray;
 import com.google.gwt.user.client.rpc.AsyncCallback;
-import java.util.Collections;
 
 /** Collection of published and draft comments loaded from the server. */
 class CommentsCollections {
@@ -159,7 +158,7 @@ class CommentsCollections {
       for (CommentInfo c : Natives.asList(in)) {
         c.path(path);
       }
-      Collections.sort(Natives.asList(in), comparing(CommentInfo::updated));
+      Natives.asList(in).sort(comparing(CommentInfo::updated));
     }
     return in;
   }

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

@@ -22,7 +22,6 @@ import com.google.gerrit.client.projects.ProjectMap;
 import com.google.gerrit.client.rpc.Natives;
 import com.google.gwt.user.client.ui.FlexTable.FlexCellFormatter;
 import com.google.gwt.user.client.ui.Image;
-import java.util.Collections;
 import java.util.List;
 
 public class ProjectsTable extends NavigationTable<ProjectInfo> {
@@ -70,7 +69,7 @@ public class ProjectsTable extends NavigationTable<ProjectInfo> {
     }
 
     List<ProjectInfo> list = Natives.asList(projects.values());
-    Collections.sort(list, comparing(ProjectInfo::name));
+    list.sort(comparing(ProjectInfo::name));
     for (ProjectInfo p : list.subList(fromIndex, toIndex)) {
       insert(table.getRowCount(), p);
     }

gerrit-gwtui/src/main/java/net/codemirror/mode/ModeInfo.java

@@ -23,7 +23,6 @@ import com.google.gwt.core.client.JsArray;
 import com.google.gwt.core.client.JsArrayString;
 import com.google.gwt.resources.client.DataResource;
 import com.google.gwt.safehtml.shared.SafeUri;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -243,7 +242,7 @@ public class ModeInfo extends JavaScriptObject {
         byMime.put(m.mode(), m);
       }
     }
-    Collections.sort(Natives.asList(filtered), comparing((ModeInfo m) -> m.name().toLowerCase()));
+    Natives.asList(filtered).sort(comparing(m -> m.name().toLowerCase()));
     setAll(filtered);
   }
 

java/com/google/gerrit/httpd/plugins/HttpPluginServlet.java

@@ -456,8 +456,8 @@ class HttpPluginServlet extends HttpServlet implements StartPluginListener, Relo
       }
     }
 
-    Collections.sort(cmds, PluginEntry.COMPARATOR_BY_NAME);
+    cmds.sort(PluginEntry.COMPARATOR_BY_NAME);
-    Collections.sort(docs, PluginEntry.COMPARATOR_BY_NAME);
+    docs.sort(PluginEntry.COMPARATOR_BY_NAME);
 
     StringBuilder md = new StringBuilder();
     md.append(String.format("# Plugin %s #\n", pluginName));

java/com/google/gerrit/index/query/AndSource.java

@@ -15,6 +15,7 @@
 package com.google.gerrit.index.query;
 
 import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.collect.ImmutableList.toImmutableList;
 
 import com.google.common.base.Throwables;
 import com.google.common.collect.FluentIterable;
@@ -26,7 +27,6 @@ import com.google.gwtorm.server.OrmRuntimeException;
 import com.google.gwtorm.server.ResultSet;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
@@ -175,10 +175,8 @@ public class AndSource<T> extends AndPredicate<T>
     return cardinality;
   }
 
-  private List<Predicate<T>> sort(Collection<? extends Predicate<T>> that) {
+  private ImmutableList<Predicate<T>> sort(Collection<? extends Predicate<T>> that) {
-    List<Predicate<T>> r = new ArrayList<>(that);
+    return that.stream().sorted(this).collect(toImmutableList());
-    Collections.sort(r, this);
-    return r;
   }
 
   @Override

java/com/google/gerrit/pgm/init/InitPlugins.java

@@ -30,7 +30,6 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 import java.util.jar.Attributes;
 import java.util.jar.JarFile;
@@ -66,7 +65,7 @@ public class InitPlugins implements InitStep {
           }
           result.add(new PluginData(pluginName, pluginVersion, tmpPlugin));
         });
-    Collections.sort(result, comparing(p -> p.name));
+    result.sort(comparing(p -> p.name));
     return result;
   }
 

java/com/google/gerrit/server/CommentsUtil.java

@@ -502,7 +502,7 @@ public class CommentsUtil {
   }
 
   private static <T extends Comment> List<T> sort(List<T> comments) {
-    Collections.sort(comments, COMMENT_ORDER);
+    comments.sort(COMMENT_ORDER);
     return comments;
   }
 

java/com/google/gerrit/server/change/WalkSorter.java

@@ -34,7 +34,6 @@ import java.io.IOException;
 import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Deque;
 import java.util.HashSet;
 import java.util.List;
@@ -110,7 +109,7 @@ public class WalkSorter {
     for (Map.Entry<Project.NameKey, Collection<ChangeData>> e : byProject.asMap().entrySet()) {
       sortedByProject.add(sortProject(e.getKey(), e.getValue()));
     }
-    Collections.sort(sortedByProject, PROJECT_LIST_SORTER);
+    sortedByProject.sort(PROJECT_LIST_SORTER);
     return Iterables.concat(sortedByProject);
   }
 

java/com/google/gerrit/server/events/EventFactory.java

@@ -73,7 +73,6 @@ import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -329,10 +328,9 @@ public class EventFactory {
       }
     }
     // Sort by original parent order.
-    Collections.sort(
+    ca.dependsOn.sort(
-        ca.dependsOn,
         comparing(
-            (DependencyAttribute d) -> {
+            d -> {
               for (int i = 0; i < parentNames.size(); i++) {
                 if (parentNames.get(i).equals(d.revision)) {
                   return i;

java/com/google/gerrit/server/git/MergeUtil.java

@@ -220,7 +220,7 @@ public class MergeUtil {
     } catch (IOException e) {
       throw new IntegrationException("Branch head sorting failed", e);
     }
-    Collections.sort(result, CodeReviewCommit.ORDER);
+    result.sort(CodeReviewCommit.ORDER);
     return result;
   }
 

java/com/google/gerrit/server/git/meta/TabFile.java

@@ -14,13 +14,15 @@
 
 package com.google.gerrit.server.git.meta;
 
+import static com.google.common.collect.ImmutableList.toImmutableList;
+
+import com.google.common.collect.ImmutableList;
 import com.google.gerrit.server.git.ValidationError;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.StringReader;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -122,10 +124,8 @@ public class TabFile {
     return buf.toString();
   }
 
-  protected static <T extends Comparable<? super T>> List<T> sort(Collection<T> m) {
+  protected static <T extends Comparable<? super T>> ImmutableList<T> sort(Collection<T> m) {
-    ArrayList<T> r = new ArrayList<>(m);
+    return m.stream().sorted().collect(toImmutableList());
-    Collections.sort(r);
-    return r;
   }
 
   protected static String pad(int len, String src) {

java/com/google/gerrit/server/mail/send/CommentSender.java

@@ -239,7 +239,7 @@ public class CommentSender extends ReplyToChangeSender {
       }
     }
 
-    Collections.sort(groups, Comparator.comparing(g -> g.filename, FilenameComparator.INSTANCE));
+    groups.sort(Comparator.comparing(g -> g.filename, FilenameComparator.INSTANCE));
     return groups;
   }
 

java/com/google/gerrit/server/notedb/ChangeNotesParser.java

@@ -79,7 +79,6 @@ import java.nio.charset.Charset;
 import java.sql.Timestamp;
 import java.text.ParseException;
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -297,9 +296,7 @@ class ChangeNotesParser {
       }
       result.put(a.getPatchSetId(), a);
     }
-    for (Collection<PatchSetApproval> v : result.asMap().values()) {
+    result.keySet().forEach(k -> result.get(k).sort(ChangeNotes.PSA_BY_TIME));
-      Collections.sort((List<PatchSetApproval>) v, ChangeNotes.PSA_BY_TIME);
-    }
     return result;
   }
 

java/com/google/gerrit/server/notedb/LegacyChangeNoteWrite.java

@@ -15,10 +15,12 @@
 package com.google.gerrit.server.notedb;
 
 import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.gerrit.server.CommentsUtil.COMMENT_ORDER;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ListMultimap;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Comment;
@@ -30,8 +32,6 @@ import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.io.PrintWriter;
 import java.sql.Timestamp;
-import java.util.ArrayList;
-import java.util.Collections;
 import java.util.Date;
 import java.util.List;
 import org.eclipse.jgit.lib.PersonIdent;
@@ -87,8 +87,7 @@ public class LegacyChangeNoteWrite {
       return;
     }
 
-    List<Integer> psIds = new ArrayList<>(comments.keySet());
+    ImmutableList<Integer> psIds = comments.keySet().stream().sorted().collect(toImmutableList());
-    Collections.sort(psIds);
 
     OutputStreamWriter streamWriter = new OutputStreamWriter(out, UTF_8);
     try (PrintWriter writer = new PrintWriter(streamWriter)) {

java/com/google/gerrit/server/patch/DiffSummaryLoader.java

@@ -19,7 +19,6 @@ import com.google.gerrit.reviewdb.client.Project;
 import com.google.inject.Inject;
 import com.google.inject.assistedinject.Assisted;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.Callable;
 
@@ -66,8 +65,9 @@ public class DiffSummaryLoader implements Callable<DiffSummary> {
           break;
       }
     }
-    Collections.sort(r);
     return new DiffSummary(
-        r.toArray(new String[r.size()]), patchList.getInsertions(), patchList.getDeletions());
+        r.stream().sorted().toArray(String[]::new),
+        patchList.getInsertions(),
+        patchList.getDeletions());
   }
 }

java/com/google/gerrit/server/patch/PatchScriptBuilder.java

@@ -35,7 +35,6 @@ import eu.medsea.mimeutil.MimeType;
 import eu.medsea.mimeutil.MimeUtil2;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Optional;
@@ -364,7 +363,7 @@ class PatchScriptBuilder {
     // them correctly later.
     //
     edits.addAll(empty);
-    Collections.sort(edits, EDIT_SORT);
+    edits.sort(EDIT_SORT);
   }
 
   private void safeAdd(List<Edit> empty, Edit toAdd) {

java/com/google/gerrit/server/permissions/SectionSortCache.java

@@ -26,7 +26,6 @@ import com.google.inject.Module;
 import com.google.inject.Singleton;
 import com.google.inject.name.Named;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.IdentityHashMap;
 import java.util.List;
 
@@ -88,7 +87,7 @@ public class SectionSortCache {
         poison |= srcMap.put(sections.get(i), i) != null;
       }
 
-      Collections.sort(sections, new MostSpecificComparator(ref));
+      sections.sort(new MostSpecificComparator(ref));
 
       int[] srcIdx;
       if (isIdentityTransform(sections, srcMap)) {

java/com/google/gerrit/server/project/ProjectConfig.java

@@ -15,6 +15,7 @@
 package com.google.gerrit.server.project;
 
 import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.gerrit.common.data.Permission.isPermission;
 import static com.google.gerrit.reviewdb.client.Project.DEFAULT_SUBMIT_TYPE;
 import static java.util.stream.Collectors.toList;
@@ -1451,10 +1452,8 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
     validationErrors.add(error);
   }
 
-  private static <T extends Comparable<? super T>> List<T> sort(Collection<T> m) {
+  private static <T extends Comparable<? super T>> ImmutableList<T> sort(Collection<T> m) {
-    ArrayList<T> r = new ArrayList<>(m);
+    return m.stream().sorted().collect(toImmutableList());
-    Collections.sort(r);
-    return r;
   }
 
   public boolean hasLegacyPermissions() {

java/com/google/gerrit/server/restapi/change/CommentJson.java

@@ -37,7 +37,6 @@ import com.google.gerrit.server.account.AccountLoader;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.inject.Inject;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.TreeMap;
@@ -98,9 +97,7 @@ class CommentJson {
         list.add(o);
       }
 
-      for (List<T> list : out.values()) {
+      out.values().forEach(l -> l.sort(COMMENT_INFO_ORDER));
-        Collections.sort(list, COMMENT_INFO_ORDER);
-      }
 
       if (loader != null) {
         loader.fill();

java/com/google/gerrit/server/restapi/change/ListRevisionDrafts.java

@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.restapi.change;
 
+import com.google.common.collect.ImmutableList;
 import com.google.gerrit.extensions.common.CommentInfo;
 import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.reviewdb.client.Comment;
@@ -61,7 +62,7 @@ public class ListRevisionDrafts implements RestReadView<RevisionResource> {
         .format(listComments(rsrc));
   }
 
-  public List<CommentInfo> getComments(RevisionResource rsrc)
+  public ImmutableList<CommentInfo> getComments(RevisionResource rsrc)
       throws OrmException, PermissionBackendException {
     return commentJson
         .get()

java/com/google/gerrit/server/restapi/change/ListRobotComments.java

@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.restapi.change;
 
+import com.google.common.collect.ImmutableList;
 import com.google.gerrit.extensions.common.RobotCommentInfo;
 import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.reviewdb.client.RobotComment;
@@ -52,7 +53,7 @@ public class ListRobotComments implements RestReadView<RevisionResource> {
         .format(listComments(rsrc));
   }
 
-  public List<RobotCommentInfo> getComments(RevisionResource rsrc)
+  public ImmutableList<RobotCommentInfo> getComments(RevisionResource rsrc)
       throws OrmException, PermissionBackendException {
     return commentJson
         .get()

java/com/google/gerrit/server/restapi/group/GetAuditLog.java

@@ -41,7 +41,6 @@ import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import org.eclipse.jgit.errors.ConfigInvalidException;
@@ -138,7 +137,7 @@ public class GetAuditLog implements RestReadView<GroupResource> {
     accountLoader.fill();
 
     // sort by date and then reverse so that the newest audit event comes first
-    Collections.sort(auditEvents, comparing((GroupAuditEventInfo a) -> a.date).reversed());
+    auditEvents.sort(comparing((GroupAuditEventInfo a) -> a.date).reversed());
     return auditEvents;
   }
 }

java/com/google/gerrit/server/restapi/group/ListSubgroups.java

@@ -30,7 +30,6 @@ import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 
 @Singleton
@@ -72,8 +71,7 @@ public class ListSubgroups implements RestReadView<GroupResource> {
         continue;
       }
     }
-    Collections.sort(
+    included.sort(
-        included,
         comparing((GroupInfo g) -> nullToEmpty(g.name)).thenComparing(g -> nullToEmpty(g.id)));
     return included;
   }

java/com/google/gerrit/server/restapi/project/ListBranches.java

@@ -46,7 +46,6 @@ import com.google.inject.Inject;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Set;
@@ -226,7 +225,7 @@ public class ListBranches implements RestReadView<ProjectResource> {
         // Do nothing.
       }
     }
-    Collections.sort(branches, new BranchComparator());
+    branches.sort(new BranchComparator());
     return branches;
   }
 

java/com/google/gerrit/server/restapi/project/ListTags.java

@@ -40,7 +40,6 @@ import com.google.inject.Inject;
 import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
@@ -135,7 +134,7 @@ public class ListTags implements RestReadView<ProjectResource> {
       }
     }
 
-    Collections.sort(tags, comparing(t -> t.ref));
+    tags.sort(comparing(t -> t.ref));
 
     return new RefFilter<TagInfo>(Constants.R_TAGS)
         .start(start)

java/com/google/gerrit/server/submit/SubmitStrategyOp.java

@@ -53,7 +53,6 @@ import com.google.gerrit.server.update.RepoContext;
 import com.google.gwtorm.server.OrmException;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -184,8 +183,7 @@ abstract class SubmitStrategyOp implements BatchUpdateOp {
         continue; // Bogus ref, can't be merged into tip so we don't care.
       }
     }
-    Collections.sort(
+    commits.sort(
-        commits,
         ReviewDbUtil.intKeyOrdering().reverse().onResultOf(CodeReviewCommit::getPatchsetId));
     CodeReviewCommit result = MergeUtil.findAnyMergedInto(rw, commits, tip);
     if (result == null) {

java/com/google/gerrit/sshd/commands/ShowConnections.java

@@ -15,8 +15,10 @@
 package com.google.gerrit.sshd.commands;
 
 import static com.google.common.base.Preconditions.checkState;
+import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.gerrit.sshd.CommandMetaData.Mode.MASTER_OR_SLAVE;
 
+import com.google.common.collect.ImmutableList;
 import com.google.gerrit.common.TimeUtil;
 import com.google.gerrit.common.data.GlobalCapability;
 import com.google.gerrit.extensions.annotations.RequiresCapability;
@@ -33,11 +35,7 @@ import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.text.SimpleDateFormat;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Comparator;
 import java.util.Date;
-import java.util.List;
 import java.util.Optional;
 import org.apache.sshd.common.io.IoAcceptor;
 import org.apache.sshd.common.io.IoSession;
@@ -92,25 +90,27 @@ final class ShowConnections extends SshCommand {
       throw new Failure(1, "fatal: sshd no longer running");
     }
 
-    final List<IoSession> list = new ArrayList<>(acceptor.getManagedSessions().values());
+    final ImmutableList<IoSession> list =
-    Collections.sort(
+        acceptor
-        list,
+            .getManagedSessions()
-        new Comparator<IoSession>() {
+            .values()
-          @Override
+            .stream()
-          public int compare(IoSession arg0, IoSession arg1) {
+            .sorted(
-            if (arg0 instanceof MinaSession) {
+                (arg0, arg1) -> {
-              MinaSession mArg0 = (MinaSession) arg0;
+                  if (arg0 instanceof MinaSession) {
-              MinaSession mArg1 = (MinaSession) arg1;
+                    MinaSession mArg0 = (MinaSession) arg0;
-              if (mArg0.getSession().getCreationTime() < mArg1.getSession().getCreationTime()) {
+                    MinaSession mArg1 = (MinaSession) arg1;
-                return -1;
+                    if (mArg0.getSession().getCreationTime()
-              } else if (mArg0.getSession().getCreationTime()
+                        < mArg1.getSession().getCreationTime()) {
-                  > mArg1.getSession().getCreationTime()) {
+                      return -1;
-                return 1;
+                    } else if (mArg0.getSession().getCreationTime()
-              }
+                        > mArg1.getSession().getCreationTime()) {
-            }
+                      return 1;
-            return (int) (arg0.getId() - arg1.getId());
+                    }
-          }
+                  }
-        });
+                  return (int) (arg0.getId() - arg1.getId());
+                })
+            .collect(toImmutableList());
 
     hostNameWidth = wide ? Integer.MAX_VALUE : columns - 9 - 9 - 10 - 32;