diff --git a/java/com/google/gerrit/extensions/api/changes/ChangeApi.java b/java/com/google/gerrit/extensions/api/changes/ChangeApi.java
index 0150e1e..dfa2128 100644
--- a/java/com/google/gerrit/extensions/api/changes/ChangeApi.java
+++ b/java/com/google/gerrit/extensions/api/changes/ChangeApi.java
@@ -49,17 +49,21 @@
    * @return API for accessing the revision.
    * @throws RestApiException if an error occurred.
    */
-  RevisionApi current() throws RestApiException;
+  default RevisionApi current() throws RestApiException {
+    return revision("current");
+  }
 
   /**
    * Look up a revision of a change by number.
    *
    * @see #current()
    */
-  RevisionApi revision(int id) throws RestApiException;
+  default RevisionApi revision(int id) throws RestApiException {
+    return revision(Integer.toString(id));
+  }
 
   /**
-   * Look up a revision of a change by commit SHA-1.
+   * Look up a revision of a change by commit SHA-1 or other supported revision string.
    *
    * @see #current()
    */
@@ -79,15 +83,23 @@
    */
   ReviewerApi reviewer(String id) throws RestApiException;
 
-  void abandon() throws RestApiException;
+  default void abandon() throws RestApiException {
+    abandon(new AbandonInput());
+  }
 
   void abandon(AbandonInput in) throws RestApiException;
 
-  void restore() throws RestApiException;
+  default void restore() throws RestApiException {
+    restore(new RestoreInput());
+  }
 
   void restore(RestoreInput in) throws RestApiException;
 
-  void move(String destination) throws RestApiException;
+  default void move(String destination) throws RestApiException {
+    MoveInput in = new MoveInput();
+    in.destinationBranch = destination;
+    move(in);
+  }
 
   void move(MoveInput in) throws RestApiException;
 
@@ -132,7 +144,9 @@
    *
    * @see Changes#id(int)
    */
-  ChangeApi revert() throws RestApiException;
+  default ChangeApi revert() throws RestApiException {
+    return revert(new RevertInput());
+  }
 
   /**
    * Create a new change that reverts this change.
@@ -144,10 +158,17 @@
   /** Create a merge patch set for the change. */
   ChangeInfo createMergePatchSet(MergePatchSetInput in) throws RestApiException;
 
-  List<ChangeInfo> submittedTogether() throws RestApiException;
+  default List<ChangeInfo> submittedTogether() throws RestApiException {
+    SubmittedTogetherInfo info =
+        submittedTogether(
+            EnumSet.noneOf(ListChangesOption.class), EnumSet.noneOf(SubmittedTogetherOption.class));
+    return info.changes;
+  }
 
-  SubmittedTogetherInfo submittedTogether(EnumSet<SubmittedTogetherOption> options)
-      throws RestApiException;
+  default SubmittedTogetherInfo submittedTogether(EnumSet<SubmittedTogetherOption> options)
+      throws RestApiException {
+    return submittedTogether(EnumSet.noneOf(ListChangesOption.class), options);
+  }
 
   SubmittedTogetherInfo submittedTogether(
       EnumSet<ListChangesOption> listOptions, EnumSet<SubmittedTogetherOption> submitOptions)
@@ -155,10 +176,14 @@
 
   /** Publishes a draft change. */
   @Deprecated
-  void publish() throws RestApiException;
+  default void publish() throws RestApiException {
+    throw new UnsupportedOperationException("draft workflow is discontinued");
+  }
 
   /** Rebase the current revision of a change using default options. */
-  void rebase() throws RestApiException;
+  default void rebase() throws RestApiException {
+    rebase(new RebaseInput());
+  }
 
   /** Rebase the current revision of a change. */
   void rebase(RebaseInput in) throws RestApiException;
@@ -172,13 +197,19 @@
 
   IncludedInInfo includedIn() throws RestApiException;
 
-  AddReviewerResult addReviewer(AddReviewerInput in) throws RestApiException;
+  default AddReviewerResult addReviewer(String reviewer) throws RestApiException {
+    AddReviewerInput in = new AddReviewerInput();
+    in.reviewer = reviewer;
+    return addReviewer(in);
+  }
 
-  AddReviewerResult addReviewer(String in) throws RestApiException;
+  AddReviewerResult addReviewer(AddReviewerInput in) throws RestApiException;
 
   SuggestedReviewersRequest suggestReviewers() throws RestApiException;
 
-  SuggestedReviewersRequest suggestReviewers(String query) throws RestApiException;
+  default SuggestedReviewersRequest suggestReviewers(String query) throws RestApiException {
+    return suggestReviewers().withQuery(query);
+  }
 
   ChangeInfo get(EnumSet<ListChangesOption> options) throws RestApiException;
 
@@ -198,10 +229,16 @@
    *   <li>{@code SKIP_MERGEABLE} is omitted, so the {@code mergeable} bit <em>is</em> set.
    * </ul>
    */
-  ChangeInfo get() throws RestApiException;
+  default ChangeInfo get() throws RestApiException {
+    return get(
+        EnumSet.complementOf(
+            EnumSet.of(ListChangesOption.CHECK, ListChangesOption.SKIP_MERGEABLE)));
+  }
 
   /** {@link #get(ListChangesOption...)} with no options included. */
-  ChangeInfo info() throws RestApiException;
+  default ChangeInfo info() throws RestApiException {
+    return get(EnumSet.noneOf(ListChangesOption.class));
+  }
 
   /**
    * Retrieve change edit when exists.
@@ -210,7 +247,9 @@
    *     ChangeEditApi#get()}.
    */
   @Deprecated
-  EditInfo getEdit() throws RestApiException;
+  default EditInfo getEdit() throws RestApiException {
+    return edit().get().orElse(null);
+  }
 
   /**
    * Provides access to an API regarding the change edit of this change.
@@ -221,7 +260,11 @@
   ChangeEditApi edit() throws RestApiException;
 
   /** Create a new patch set with a new commit message. */
-  void setMessage(String message) throws RestApiException;
+  default void setMessage(String message) throws RestApiException {
+    CommitMessageInput in = new CommitMessageInput();
+    in.message = message;
+    setMessage(in);
+  }
 
   /** Create a new patch set with a new commit message. */
   void setMessage(CommitMessageInput in) throws RestApiException;
@@ -347,16 +390,6 @@
     }
 
     @Override
-    public RevisionApi current() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
-    public RevisionApi revision(int id) throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public ReviewerApi reviewer(String id) throws RestApiException {
       throw new NotImplementedException();
     }
@@ -367,31 +400,16 @@
     }
 
     @Override
-    public void abandon() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public void abandon(AbandonInput in) throws RestApiException {
       throw new NotImplementedException();
     }
 
     @Override
-    public void restore() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public void restore(RestoreInput in) throws RestApiException {
       throw new NotImplementedException();
     }
 
     @Override
-    public void move(String destination) throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public void move(MoveInput in) throws RestApiException {
       throw new NotImplementedException();
     }
@@ -412,27 +430,11 @@
     }
 
     @Override
-    public ChangeApi revert() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public ChangeApi revert(RevertInput in) throws RestApiException {
       throw new NotImplementedException();
     }
 
     @Override
-    public void publish() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Deprecated
-    @Override
-    public void rebase() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public void rebase(RebaseInput in) throws RestApiException {
       throw new NotImplementedException();
     }
@@ -463,51 +465,21 @@
     }
 
     @Override
-    public AddReviewerResult addReviewer(String in) throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public SuggestedReviewersRequest suggestReviewers() throws RestApiException {
       throw new NotImplementedException();
     }
 
     @Override
-    public SuggestedReviewersRequest suggestReviewers(String query) throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public ChangeInfo get(EnumSet<ListChangesOption> options) throws RestApiException {
       throw new NotImplementedException();
     }
 
     @Override
-    public ChangeInfo get() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
-    public ChangeInfo info() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
-    public void setMessage(String message) throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public void setMessage(CommitMessageInput in) throws RestApiException {
       throw new NotImplementedException();
     }
 
     @Override
-    public EditInfo getEdit() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public ChangeEditApi edit() throws RestApiException {
       throw new NotImplementedException();
     }
diff --git a/java/com/google/gerrit/extensions/api/changes/RevisionApi.java b/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
index 75cf3a6..14dc589 100644
--- a/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
+++ b/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
@@ -14,6 +14,7 @@
 
 package com.google.gerrit.extensions.api.changes;
 
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.extensions.client.SubmitType;
 import com.google.gerrit.extensions.common.ActionInfo;
 import com.google.gerrit.extensions.common.CherryPickChangeInfo;
@@ -34,7 +35,9 @@
 
 public interface RevisionApi {
   @Deprecated
-  void delete() throws RestApiException;
+  default void delete() throws RestApiException {
+    throw new UnsupportedOperationException("draft workflow is discontinued");
+  }
 
   String description() throws RestApiException;
 
@@ -42,22 +45,32 @@
 
   ReviewResult review(ReviewInput in) throws RestApiException;
 
-  void submit() throws RestApiException;
+  default void submit() throws RestApiException {
+    SubmitInput in = new SubmitInput();
+    submit(in);
+  }
 
   void submit(SubmitInput in) throws RestApiException;
 
-  BinaryResult submitPreview() throws RestApiException;
+  default BinaryResult submitPreview() throws RestApiException {
+    return submitPreview("zip");
+  }
 
   BinaryResult submitPreview(String format) throws RestApiException;
 
   @Deprecated
-  void publish() throws RestApiException;
+  default void publish() throws RestApiException {
+    throw new UnsupportedOperationException("draft workflow is discontinued");
+  }
 
   ChangeApi cherryPick(CherryPickInput in) throws RestApiException;
 
   CherryPickChangeInfo cherryPickAsInfo(CherryPickInput in) throws RestApiException;
 
-  ChangeApi rebase() throws RestApiException;
+  default ChangeApi rebase() throws RestApiException {
+    RebaseInput in = new RebaseInput();
+    return rebase(in);
+  }
 
   ChangeApi rebase(RebaseInput in) throws RestApiException;
 
@@ -69,9 +82,11 @@
 
   Set<String> reviewed() throws RestApiException;
 
-  Map<String, FileInfo> files() throws RestApiException;
+  default Map<String, FileInfo> files() throws RestApiException {
+    return files(null);
+  }
 
-  Map<String, FileInfo> files(String base) throws RestApiException;
+  Map<String, FileInfo> files(@Nullable String base) throws RestApiException;
 
   Map<String, FileInfo> files(int parentNum) throws RestApiException;
 
@@ -165,33 +180,16 @@
    * interface.
    */
   class NotImplemented implements RevisionApi {
-    @Deprecated
-    @Override
-    public void delete() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
     @Override
     public ReviewResult review(ReviewInput in) throws RestApiException {
       throw new NotImplementedException();
     }
 
     @Override
-    public void submit() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public void submit(SubmitInput in) throws RestApiException {
       throw new NotImplementedException();
     }
 
-    @Deprecated
-    @Override
-    public void publish() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
     @Override
     public ChangeApi cherryPick(CherryPickInput in) throws RestApiException {
       throw new NotImplementedException();
@@ -203,11 +201,6 @@
     }
 
     @Override
-    public ChangeApi rebase() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public ChangeApi rebase(RebaseInput in) throws RestApiException {
       throw new NotImplementedException();
     }
@@ -253,11 +246,6 @@
     }
 
     @Override
-    public Map<String, FileInfo> files() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public List<String> queryFiles(String query) throws RestApiException {
       throw new NotImplementedException();
     }
@@ -348,11 +336,6 @@
     }
 
     @Override
-    public BinaryResult submitPreview() throws RestApiException {
-      throw new NotImplementedException();
-    }
-
-    @Override
     public BinaryResult submitPreview(String format) throws RestApiException {
       throw new NotImplementedException();
     }
diff --git a/java/com/google/gerrit/server/api/changes/ChangeApiImpl.java b/java/com/google/gerrit/server/api/changes/ChangeApiImpl.java
index 358a3a8..0f731ed 100644
--- a/java/com/google/gerrit/server/api/changes/ChangeApiImpl.java
+++ b/java/com/google/gerrit/server/api/changes/ChangeApiImpl.java
@@ -43,7 +43,6 @@
 import com.google.gerrit.extensions.common.ChangeMessageInfo;
 import com.google.gerrit.extensions.common.CommentInfo;
 import com.google.gerrit.extensions.common.CommitMessageInput;
-import com.google.gerrit.extensions.common.EditInfo;
 import com.google.gerrit.extensions.common.Input;
 import com.google.gerrit.extensions.common.MergePatchSetInput;
 import com.google.gerrit.extensions.common.PureRevertInfo;
@@ -256,16 +255,6 @@
   }
 
   @Override
-  public RevisionApi current() throws RestApiException {
-    return revision("current");
-  }
-
-  @Override
-  public RevisionApi revision(int id) throws RestApiException {
-    return revision(String.valueOf(id));
-  }
-
-  @Override
   public RevisionApi revision(String id) throws RestApiException {
     try {
       return revisionApi.create(revisions.parse(change, IdString.fromDecoded(id)));
@@ -284,11 +273,6 @@
   }
 
   @Override
-  public void abandon() throws RestApiException {
-    abandon(new AbandonInput());
-  }
-
-  @Override
   public void abandon(AbandonInput in) throws RestApiException {
     try {
       abandon.apply(change, in);
@@ -298,11 +282,6 @@
   }
 
   @Override
-  public void restore() throws RestApiException {
-    restore(new RestoreInput());
-  }
-
-  @Override
   public void restore(RestoreInput in) throws RestApiException {
     try {
       restore.apply(change, in);
@@ -312,13 +291,6 @@
   }
 
   @Override
-  public void move(String destination) throws RestApiException {
-    MoveInput in = new MoveInput();
-    in.destinationBranch = destination;
-    move(in);
-  }
-
-  @Override
   public void move(MoveInput in) throws RestApiException {
     try {
       move.apply(change, in);
@@ -360,11 +332,6 @@
   }
 
   @Override
-  public ChangeApi revert() throws RestApiException {
-    return revert(new RevertInput());
-  }
-
-  @Override
   public ChangeApi revert(RevertInput in) throws RestApiException {
     try {
       return changeApi.id(revert.apply(change, in)._number);
@@ -383,20 +350,6 @@
   }
 
   @Override
-  public List<ChangeInfo> submittedTogether() throws RestApiException {
-    SubmittedTogetherInfo info =
-        submittedTogether(
-            EnumSet.noneOf(ListChangesOption.class), EnumSet.noneOf(SubmittedTogetherOption.class));
-    return info.changes;
-  }
-
-  @Override
-  public SubmittedTogetherInfo submittedTogether(EnumSet<SubmittedTogetherOption> options)
-      throws RestApiException {
-    return submittedTogether(EnumSet.noneOf(ListChangesOption.class), options);
-  }
-
-  @Override
   public SubmittedTogetherInfo submittedTogether(
       EnumSet<ListChangesOption> listOptions, EnumSet<SubmittedTogetherOption> submitOptions)
       throws RestApiException {
@@ -411,17 +364,6 @@
     }
   }
 
-  @Deprecated
-  @Override
-  public void publish() throws RestApiException {
-    throw new UnsupportedOperationException("draft workflow is discontinued");
-  }
-
-  @Override
-  public void rebase() throws RestApiException {
-    rebase(new RebaseInput());
-  }
-
   @Override
   public void rebase(RebaseInput in) throws RestApiException {
     try {
@@ -466,13 +408,6 @@
   }
 
   @Override
-  public AddReviewerResult addReviewer(String reviewer) throws RestApiException {
-    AddReviewerInput in = new AddReviewerInput();
-    in.reviewer = reviewer;
-    return addReviewer(in);
-  }
-
-  @Override
   public AddReviewerResult addReviewer(AddReviewerInput in) throws RestApiException {
     try {
       return postReviewers.apply(change, in);
@@ -491,11 +426,6 @@
     };
   }
 
-  @Override
-  public SuggestedReviewersRequest suggestReviewers(String query) throws RestApiException {
-    return suggestReviewers().withQuery(query);
-  }
-
   private List<SuggestedReviewerInfo> suggestReviewers(SuggestedReviewersRequest r)
       throws RestApiException {
     try {
@@ -517,30 +447,11 @@
   }
 
   @Override
-  public ChangeInfo get() throws RestApiException {
-    return get(
-        EnumSet.complementOf(
-            EnumSet.of(ListChangesOption.CHECK, ListChangesOption.SKIP_MERGEABLE)));
-  }
-
-  @Override
-  public EditInfo getEdit() throws RestApiException {
-    return edit().get().orElse(null);
-  }
-
-  @Override
   public ChangeEditApi edit() throws RestApiException {
     return changeEditApi.create(change);
   }
 
   @Override
-  public void setMessage(String msg) throws RestApiException {
-    CommitMessageInput in = new CommitMessageInput();
-    in.message = msg;
-    setMessage(in);
-  }
-
-  @Override
   public void setMessage(CommitMessageInput in) throws RestApiException {
     try {
       putMessage.apply(change, in);
@@ -550,11 +461,6 @@
   }
 
   @Override
-  public ChangeInfo info() throws RestApiException {
-    return get(EnumSet.noneOf(ListChangesOption.class));
-  }
-
-  @Override
   public void setHashtags(HashtagsInput input) throws RestApiException {
     try {
       postHashtags.apply(change, input);
diff --git a/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java b/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
index 3f03b57..f8a2ecb 100644
--- a/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
+++ b/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
@@ -18,6 +18,7 @@
 import static com.google.gerrit.server.api.ApiUtil.asRestApiException;
 
 import com.google.common.collect.ImmutableSet;
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.extensions.api.changes.ChangeApi;
 import com.google.gerrit.extensions.api.changes.Changes;
 import com.google.gerrit.extensions.api.changes.CherryPickInput;
@@ -227,12 +228,6 @@
   }
 
   @Override
-  public void submit() throws RestApiException {
-    SubmitInput in = new SubmitInput();
-    submit(in);
-  }
-
-  @Override
   public void submit(SubmitInput in) throws RestApiException {
     try {
       submit.apply(revision, in);
@@ -242,11 +237,6 @@
   }
 
   @Override
-  public BinaryResult submitPreview() throws RestApiException {
-    return submitPreview("zip");
-  }
-
-  @Override
   public BinaryResult submitPreview(String format) throws RestApiException {
     try {
       submitPreview.setFormat(format);
@@ -257,22 +247,6 @@
   }
 
   @Override
-  public void publish() throws RestApiException {
-    throw new UnsupportedOperationException("draft workflow is discontinued");
-  }
-
-  @Override
-  public void delete() throws RestApiException {
-    throw new UnsupportedOperationException("draft workflow is discontinued");
-  }
-
-  @Override
-  public ChangeApi rebase() throws RestApiException {
-    RebaseInput in = new RebaseInput();
-    return rebase(in);
-  }
-
-  @Override
   public ChangeApi rebase(RebaseInput in) throws RestApiException {
     try {
       return changes.id(rebase.apply(revision, in)._number);
@@ -366,17 +340,7 @@
 
   @SuppressWarnings("unchecked")
   @Override
-  public Map<String, FileInfo> files() throws RestApiException {
-    try {
-      return (Map<String, FileInfo>) listFiles.apply(revision).value();
-    } catch (Exception e) {
-      throw asRestApiException("Cannot retrieve files", e);
-    }
-  }
-
-  @SuppressWarnings("unchecked")
-  @Override
-  public Map<String, FileInfo> files(String base) throws RestApiException {
+  public Map<String, FileInfo> files(@Nullable String base) throws RestApiException {
     try {
       return (Map<String, FileInfo>) listFiles.setBase(base).apply(revision).value();
     } catch (Exception e) {
diff --git a/java/com/google/gerrit/server/restapi/change/Files.java b/java/com/google/gerrit/server/restapi/change/Files.java
index 1bb6bf2..b374fdc 100644
--- a/java/com/google/gerrit/server/restapi/change/Files.java
+++ b/java/com/google/gerrit/server/restapi/change/Files.java
@@ -18,6 +18,7 @@
 import com.google.common.flogger.FluentLogger;
 import com.google.common.hash.Hasher;
 import com.google.common.hash.Hashing;
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.extensions.common.FileInfo;
 import com.google.gerrit.extensions.registration.DynamicMap;
 import com.google.gerrit.extensions.restapi.AuthException;
@@ -332,7 +333,7 @@
       return this;
     }
 
-    public ListFiles setBase(String base) {
+    public ListFiles setBase(@Nullable String base) {
       this.base = base;
       return this;
     }