diff --git a/gerrit-server/src/main/java/com/google/gerrit/metrics/Field.java b/gerrit-server/src/main/java/com/google/gerrit/metrics/Field.java
index 364f4f8..95fbf04 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/metrics/Field.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/metrics/Field.java
@@ -161,17 +161,10 @@
   private static <T> Function<T, String> initFormatter(Class<T> keyType) {
     if (keyType == String.class) {
       return (Function<T, String>) Functions.<String> identity();
-
     } else if (keyType == Integer.class || keyType == Boolean.class) {
       return (Function<T, String>) Functions.toStringFunction();
-
     } else if (Enum.class.isAssignableFrom(keyType)) {
-      return new Function<T, String>() {
-        @Override
-        public String apply(T in) {
-          return ((Enum<?>) in).name();
-        }
-      };
+      return in -> ((Enum<?>) in).name();
     }
     throw new IllegalStateException("unsupported type " + keyType.getName());
   }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedCallback.java b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedCallback.java
index e7ab75c..d3fe6ed 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedCallback.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedCallback.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.metrics.dropwizard;
 
-import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Maps;
 import com.google.gerrit.metrics.Description;
@@ -124,14 +123,7 @@
 
   @Override
   public Map<Object, Metric> getCells() {
-    return Maps.transformValues(
-        cells,
-        new Function<ValueGauge, Metric> () {
-          @Override
-          public Metric apply(ValueGauge in) {
-            return in;
-          }
-        });
+    return Maps.transformValues(cells, in -> (Metric) in);
   }
 
   final class ValueGauge implements Gauge<V> {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedCounter.java b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedCounter.java
index 10b92e6..7894a84 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedCounter.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedCounter.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.metrics.dropwizard;
 
-import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Maps;
 import com.google.gerrit.metrics.Description;
@@ -98,13 +97,6 @@
 
   @Override
   public Map<Object, Metric> getCells() {
-    return Maps.transformValues(
-        cells,
-        new Function<CounterImpl, Metric> () {
-          @Override
-          public Metric apply(CounterImpl in) {
-            return in.metric;
-          }
-        });
+    return Maps.transformValues(cells, c -> c.metric);
   }
 }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedHistogram.java b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedHistogram.java
index 071c678..ff38cd4 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedHistogram.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedHistogram.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.metrics.dropwizard;
 
-import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Maps;
 import com.google.gerrit.metrics.Description;
@@ -96,13 +95,6 @@
 
   @Override
   public Map<Object, Metric> getCells() {
-    return Maps.transformValues(
-        cells,
-        new Function<HistogramImpl, Metric> () {
-          @Override
-          public Metric apply(HistogramImpl in) {
-            return in.metric;
-          }
-        });
+    return Maps.transformValues(cells, h -> h.metric);
   }
 }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedTimer.java b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedTimer.java
index 6981ef1..aff6c4a 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedTimer.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/BucketedTimer.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.metrics.dropwizard;
 
-import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Maps;
 import com.google.gerrit.metrics.Description;
@@ -96,13 +95,6 @@
 
   @Override
   public Map<Object, Metric> getCells() {
-    return Maps.transformValues(
-        cells,
-        new Function<TimerImpl, Metric> () {
-          @Override
-          public Metric apply(TimerImpl in) {
-            return in.metric;
-          }
-        });
+    return Maps.transformValues(cells, t -> t.metric);
   }
 }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/DropWizardMetricMaker.java b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/DropWizardMetricMaker.java
index e159c82..ee2ce29 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/DropWizardMetricMaker.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/metrics/dropwizard/DropWizardMetricMaker.java
@@ -18,7 +18,6 @@
 import static com.google.gerrit.metrics.dropwizard.MetricResource.METRIC_KIND;
 import static com.google.gerrit.server.config.ConfigResource.CONFIG_KIND;
 
-import com.google.common.base.Function;
 import com.google.common.collect.FluentIterable;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
@@ -304,14 +303,8 @@
   @Override
   public synchronized RegistrationHandle newTrigger(
       Set<CallbackMetric<?>> metrics, Runnable trigger) {
-    final ImmutableSet<CallbackMetricGlue> all = FluentIterable.from(metrics)
-        .transform(
-          new Function<CallbackMetric<?>, CallbackMetricGlue>() {
-            @Override
-            public CallbackMetricGlue apply(CallbackMetric<?> input) {
-              return (CallbackMetricGlue) input;
-            }
-          })
+    ImmutableSet<CallbackMetricGlue> all = FluentIterable.from(metrics)
+        .transform(m -> (CallbackMetricGlue) m)
         .toSet();
 
     trigger = new CallbackGroup(trigger, all);
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java b/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java
index 5c0723a..bbc7ced 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java
@@ -16,9 +16,9 @@
 
 import static com.google.gerrit.server.notedb.ReviewerStateInternal.CC;
 import static com.google.gerrit.server.notedb.ReviewerStateInternal.REVIEWER;
+import static java.util.Comparator.comparing;
 
 import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Function;
 import com.google.common.base.Predicate;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableListMultimap;
@@ -52,7 +52,6 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.sql.Timestamp;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -81,14 +80,7 @@
       LoggerFactory.getLogger(ApprovalsUtil.class);
 
   private static final Ordering<PatchSetApproval> SORT_APPROVALS =
-      Ordering.natural()
-          .onResultOf(
-              new Function<PatchSetApproval, Timestamp>() {
-                @Override
-                public Timestamp apply(PatchSetApproval a) {
-                  return a.getGranted();
-                }
-              });
+      Ordering.from(comparing(PatchSetApproval::getGranted));
 
   public static List<PatchSetApproval> sortApprovals(
       Iterable<PatchSetApproval> approvals) {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/AccountResolver.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/AccountResolver.java
index 5a18269..b400eb7 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/AccountResolver.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/AccountResolver.java
@@ -14,8 +14,8 @@
 
 package com.google.gerrit.server.account;
 
-import com.google.common.base.Function;
-import com.google.common.collect.FluentIterable;
+import static java.util.stream.Collectors.toSet;
+
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.AccountExternalId;
 import com.google.gerrit.reviewdb.server.ReviewDb;
@@ -191,14 +191,9 @@
 
       // At this point we have no clue. Just perform a whole bunch of suggestions
       // and pray we come up with a reasonable result list.
-      return FluentIterable
-          .from(accountQueryProvider.get().byDefault(nameOrEmail))
-          .transform(new Function<AccountState, Account.Id>() {
-            @Override
-            public Account.Id apply(AccountState accountState) {
-              return accountState.getAccount().getId();
-            }
-          }).toSet();
+      return accountQueryProvider.get().byDefault(nameOrEmail).stream()
+          .map(a -> a.getAccount().getId())
+          .collect(toSet());
     }
 
     List<Account> m = db.accounts().byFullName(nameOrEmail).toList();
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/AccountState.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/AccountState.java
index 05a7179..ed99266 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/AccountState.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/AccountState.java
@@ -36,12 +36,7 @@
 
 public class AccountState {
   public static final Function<AccountState, Account.Id> ACCOUNT_ID_FUNCTION =
-      new Function<AccountState, Account.Id>() {
-        @Override
-        public Account.Id apply(AccountState in) {
-          return in.getAccount().getId();
-        }
-      };
+      a -> a.getAccount().getId();
 
   private final Account account;
   private final Set<AccountGroup.UUID> internalGroups;
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/CapabilityControl.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/CapabilityControl.java
index e348e73..d86d27c 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/CapabilityControl.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/CapabilityControl.java
@@ -14,15 +14,14 @@
 
 package com.google.gerrit.server.account;
 
-import com.google.common.base.Function;
+import static com.google.common.base.Predicates.not;
+
 import com.google.common.base.Predicate;
-import com.google.common.base.Predicates;
-import com.google.common.collect.Iterables;
+import com.google.common.collect.FluentIterable;
 import com.google.gerrit.common.data.GlobalCapability;
 import com.google.gerrit.common.data.PermissionRange;
 import com.google.gerrit.common.data.PermissionRule;
 import com.google.gerrit.common.data.PermissionRule.Action;
-import com.google.gerrit.reviewdb.client.AccountGroup;
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.PeerDaemonUser;
 import com.google.gerrit.server.git.QueueProvider;
@@ -32,6 +31,7 @@
 import com.google.inject.assistedinject.Assisted;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -98,7 +98,7 @@
     if (canEmailReviewers == null) {
       canEmailReviewers =
           matchAny(capabilities.emailReviewers, ALLOWED_RULE)
-          || !matchAny(capabilities.emailReviewers, Predicates.not(ALLOWED_RULE));
+          || !matchAny(capabilities.emailReviewers, not(ALLOWED_RULE));
 
     }
     return canEmailReviewers;
@@ -279,23 +279,16 @@
     return mine;
   }
 
-  private static final Predicate<PermissionRule> ALLOWED_RULE = new Predicate<PermissionRule>() {
-    @Override
-    public boolean apply(PermissionRule rule) {
-      return rule.getAction() == Action.ALLOW;
-    }
-  };
+  private static final Predicate<PermissionRule> ALLOWED_RULE =
+      r -> r.getAction() == Action.ALLOW;
 
-  private boolean matchAny(Iterable<PermissionRule> rules, Predicate<PermissionRule> predicate) {
-    Iterable<AccountGroup.UUID> ids = Iterables.transform(
-        Iterables.filter(rules, predicate),
-        new Function<PermissionRule, AccountGroup.UUID>() {
-          @Override
-          public AccountGroup.UUID apply(PermissionRule rule) {
-            return rule.getGroup().getUUID();
-          }
-        });
-    return user.getEffectiveGroups().containsAnyOf(ids);
+  private boolean matchAny(Collection<PermissionRule> rules,
+      Predicate<PermissionRule> predicate) {
+    return user.getEffectiveGroups()
+        .containsAnyOf(
+            FluentIterable.from(rules)
+                .filter(predicate)
+                .transform(r -> r.getGroup().getUUID()));
   }
 
   private static boolean match(GroupMembership groups,
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/DeleteWatchedProjects.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/DeleteWatchedProjects.java
index e2fbc3c..0e9bc2e 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/DeleteWatchedProjects.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/DeleteWatchedProjects.java
@@ -14,8 +14,8 @@
 
 package com.google.gerrit.server.account;
 
-import com.google.common.base.Function;
-import com.google.common.collect.Lists;
+import static java.util.stream.Collectors.toList;
+
 import com.google.gerrit.extensions.client.ProjectWatchInfo;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.Response;
@@ -105,13 +105,10 @@
 
   private void deleteFromGit(Account.Id accountId, List<ProjectWatchInfo> input)
       throws IOException, ConfigInvalidException {
-    watchConfig.deleteProjectWatches(accountId, Lists.transform(input,
-        new Function<ProjectWatchInfo, ProjectWatchKey>() {
-          @Override
-          public ProjectWatchKey apply(ProjectWatchInfo info) {
-            return ProjectWatchKey.create(new Project.NameKey(info.project),
-                info.filter);
-          }
-        }));
+    watchConfig.deleteProjectWatches(
+        accountId,
+        input.stream().map(w -> ProjectWatchKey.create(
+                new Project.NameKey(w.project), w.filter))
+            .collect(toList()));
   }
 }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/GetSshKeys.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/GetSshKeys.java
index bf1a3af..df125e0 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/GetSshKeys.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/GetSshKeys.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.server.account;
 
-import com.google.common.base.Function;
 import com.google.common.base.Strings;
 import com.google.common.collect.Lists;
 import com.google.gerrit.extensions.common.SshKeyInfo;
@@ -60,13 +59,9 @@
 
   public List<SshKeyInfo> apply(IdentifiedUser user)
       throws RepositoryNotFoundException, IOException, ConfigInvalidException {
-    return Lists.transform(authorizedKeys.getKeys(user.getAccountId()),
-        new Function<AccountSshKey, SshKeyInfo>() {
-          @Override
-          public SshKeyInfo apply(AccountSshKey key) {
-            return newSshKeyInfo(key);
-          }
-        });
+    return Lists.transform(
+        authorizedKeys.getKeys(user.getAccountId()),
+        GetSshKeys::newSshKeyInfo);
   }
 
   public static SshKeyInfo newSshKeyInfo(AccountSshKey sshKey) {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/InternalGroupBackend.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/InternalGroupBackend.java
index c47d6f8..84660ec 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/InternalGroupBackend.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/InternalGroupBackend.java
@@ -14,10 +14,8 @@
 
 package com.google.gerrit.server.account;
 
-import com.google.common.base.Function;
-import com.google.common.base.Predicate;
-import com.google.common.collect.Iterables;
-import com.google.common.collect.Lists;
+import static java.util.stream.Collectors.toList;
+
 import com.google.gerrit.common.data.GroupDescription;
 import com.google.gerrit.common.data.GroupDescriptions;
 import com.google.gerrit.common.data.GroupReference;
@@ -30,18 +28,11 @@
 import org.eclipse.jgit.lib.ObjectId;
 
 import java.util.Collection;
+import java.util.stream.StreamSupport;
 
 /** Implementation of GroupBackend for the internal group system. */
 @Singleton
 public class InternalGroupBackend implements GroupBackend {
-  private static final Function<AccountGroup, GroupReference> ACT_GROUP_TO_GROUP_REF =
-      new Function<AccountGroup, GroupReference>() {
-        @Override
-        public GroupReference apply(AccountGroup group) {
-          return GroupReference.forGroup(group);
-        }
-      };
-
   private final GroupControl.Factory groupControlFactory;
   private final GroupCache groupCache;
   private final IncludingGroupMembership.Factory groupMembershipFactory;
@@ -77,16 +68,13 @@
   @Override
   public Collection<GroupReference> suggest(final String name,
       final ProjectControl project) {
-    Iterable<AccountGroup> filtered = Iterables.filter(groupCache.all(),
-        new Predicate<AccountGroup>() {
-          @Override
-          public boolean apply(AccountGroup group) {
+    return StreamSupport.stream(groupCache.all().spliterator(), false)
+        .filter(group ->
             // startsWithIgnoreCase && isVisible
-            return group.getName().regionMatches(true, 0, name, 0, name.length())
-                && groupControlFactory.controlFor(group).isVisible();
-          }
-        });
-    return Lists.newArrayList(Iterables.transform(filtered, ACT_GROUP_TO_GROUP_REF));
+            group.getName().regionMatches(true, 0, name, 0, name.length())
+                && groupControlFactory.controlFor(group).isVisible())
+        .map(GroupReference::forGroup)
+        .collect(toList());
   }
 
   @Override
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/VersionedAuthorizedKeys.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/VersionedAuthorizedKeys.java
index 30a3bdf..871b1cd 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/VersionedAuthorizedKeys.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/VersionedAuthorizedKeys.java
@@ -15,8 +15,8 @@
 package com.google.gerrit.server.account;
 
 import static com.google.common.base.Preconditions.checkState;
+import static java.util.Comparator.comparing;
 
-import com.google.common.base.Function;
 import com.google.common.base.Optional;
 import com.google.common.base.Strings;
 import com.google.common.collect.Lists;
@@ -278,13 +278,7 @@
    * @param newKeys the new public SSH keys
    */
   public void setKeys(Collection<AccountSshKey> newKeys) {
-    Ordering<AccountSshKey> o =
-        Ordering.natural().onResultOf(new Function<AccountSshKey, Integer>() {
-          @Override
-          public Integer apply(AccountSshKey sshKey) {
-            return sshKey.getKey().get();
-          }
-        });
+    Ordering<AccountSshKey> o = Ordering.from(comparing(k -> k.getKey().get()));
     keys = new ArrayList<>(Collections.nCopies(o.max(newKeys).getKey().get(),
         Optional.<AccountSshKey> absent()));
     for (AccountSshKey key : newKeys) {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/config/GetServerInfo.java b/gerrit-server/src/main/java/com/google/gerrit/server/config/GetServerInfo.java
index 14c6da7..4d15a2f 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/config/GetServerInfo.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/config/GetServerInfo.java
@@ -14,11 +14,11 @@
 
 package com.google.gerrit.server.config;
 
+import static java.util.stream.Collectors.toList;
+
 import com.google.common.base.CharMatcher;
-import com.google.common.base.Function;
 import com.google.common.base.Optional;
 import com.google.common.base.Strings;
-import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import com.google.gerrit.common.data.ContributorAgreement;
 import com.google.gerrit.extensions.common.AuthInfo;
@@ -225,14 +225,8 @@
             getDownloadSchemeInfo(scheme, downloadCommands, cloneCommands));
       }
     }
-    info.archives = Lists.newArrayList(Iterables.transform(
-        archiveFormats.getAllowed(),
-        new Function<ArchiveFormat, String>() {
-          @Override
-          public String apply(ArchiveFormat in) {
-            return in.getShortName();
-          }
-        }));
+    info.archives = archiveFormats.getAllowed().stream()
+        .map(ArchiveFormat::getShortName).collect(toList());
     return info;
   }
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/config/ProjectConfigEntry.java b/gerrit-server/src/main/java/com/google/gerrit/server/config/ProjectConfigEntry.java
index cc7857c..7d11ff4 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/config/ProjectConfigEntry.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/config/ProjectConfigEntry.java
@@ -14,8 +14,8 @@
 
 package com.google.gerrit.server.config;
 
-import com.google.common.base.Function;
-import com.google.common.collect.Lists;
+import static java.util.stream.Collectors.toList;
+
 import com.google.gerrit.extensions.annotations.ExtensionPoint;
 import com.google.gerrit.extensions.api.projects.ConfigValue;
 import com.google.gerrit.extensions.api.projects.ProjectConfigEntryType;
@@ -137,14 +137,9 @@
       T defaultValue, Class<T> permittedValues, boolean inheritable,
       String description) {
     this(displayName, defaultValue.name(), ProjectConfigEntryType.LIST,
-        Lists.transform(
-            Arrays.asList(permittedValues.getEnumConstants()),
-            new Function<Enum<?>, String>() {
-              @Override
-              public String apply(Enum<?> e) {
-                return e.name();
-              }
-            }), inheritable, description);
+        Arrays.stream(permittedValues.getEnumConstants())
+            .map(Enum::name).collect(toList()),
+        inheritable, description);
   }
 
   public ProjectConfigEntry(String displayName, String defaultValue,
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerAdded.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerAdded.java
index 35b14dc..9dbbeef 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerAdded.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerAdded.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.server.extensions.events;
 
-import com.google.common.base.Function;
 import com.google.common.collect.Lists;
 import com.google.gerrit.extensions.api.changes.NotifyHandling;
 import com.google.gerrit.extensions.common.AccountInfo;
@@ -72,18 +71,10 @@
       return;
     }
 
-    List<AccountInfo> transformed = Lists.transform(reviewers,
-        new Function<Account.Id, AccountInfo>() {
-          @Override
-          public AccountInfo apply(Account.Id account) {
-            return util.accountInfo(account);
-          }
-        });
-
     try {
       fire(util.changeInfo(change),
           util.revisionInfo(change.getProject(), patchSet),
-          transformed,
+          Lists.transform(reviewers, util::accountInfo),
           util.accountInfo(adder),
           when);
     } catch (PatchListNotAvailableException | GpgException | IOException
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/webui/UiActions.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/webui/UiActions.java
index 601bcc6..3dbd1e3 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/webui/UiActions.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/webui/UiActions.java
@@ -14,11 +14,8 @@
 
 package com.google.gerrit.server.extensions.webui;
 
-import com.google.common.base.Function;
 import com.google.common.base.Predicate;
-import com.google.common.base.Predicates;
-import com.google.common.collect.Iterables;
-import com.google.gerrit.common.Nullable;
+import com.google.common.collect.FluentIterable;
 import com.google.gerrit.extensions.registration.DynamicMap;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.RestCollection;
@@ -33,16 +30,13 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.Objects;
+
 public class UiActions {
   private static final Logger log = LoggerFactory.getLogger(UiActions.class);
 
   public static Predicate<UiAction.Description> enabled() {
-    return new Predicate<UiAction.Description>() {
-      @Override
-      public boolean apply(UiAction.Description input) {
-        return input.isEnabled();
-      }
-    };
+    return UiAction.Description::isEnabled;
   }
 
   public static <R extends RestResource> Iterable<UiAction.Description> from(
@@ -56,58 +50,52 @@
       DynamicMap<RestView<R>> views,
       final R resource,
       final Provider<CurrentUser> userProvider) {
-    return Iterables.filter(
-      Iterables.transform(
-        views,
-        new Function<DynamicMap.Entry<RestView<R>>, UiAction.Description> () {
-          @Override
-          @Nullable
-          public UiAction.Description apply(DynamicMap.Entry<RestView<R>> e) {
-            int d = e.getExportName().indexOf('.');
-            if (d < 0) {
-              return null;
-            }
+    return FluentIterable.from(views)
+        .transform((DynamicMap.Entry<RestView<R>> e) -> {
+              int d = e.getExportName().indexOf('.');
+              if (d < 0) {
+                return null;
+              }
 
-            RestView<R> view;
-            try {
-              view = e.getProvider().get();
-            } catch (RuntimeException err) {
-              log.error(String.format(
-                  "error creating view %s.%s",
-                  e.getPluginName(), e.getExportName()), err);
-              return null;
-            }
+              RestView<R> view;
+              try {
+                view = e.getProvider().get();
+              } catch (RuntimeException err) {
+                log.error(String.format(
+                    "error creating view %s.%s",
+                    e.getPluginName(), e.getExportName()), err);
+                return null;
+              }
 
-            if (!(view instanceof UiAction)) {
-              return null;
-            }
+              if (!(view instanceof UiAction)) {
+                return null;
+              }
 
-            try {
-              CapabilityUtils.checkRequiresCapability(userProvider,
-                  e.getPluginName(), view.getClass());
-            } catch (AuthException exc) {
-              return null;
-            }
+              try {
+                CapabilityUtils.checkRequiresCapability(userProvider,
+                    e.getPluginName(), view.getClass());
+              } catch (AuthException exc) {
+                return null;
+              }
 
-            UiAction.Description dsc =
-                ((UiAction<R>) view).getDescription(resource);
-            if (dsc == null || !dsc.isVisible()) {
-              return null;
-            }
+              UiAction.Description dsc =
+                  ((UiAction<R>) view).getDescription(resource);
+              if (dsc == null || !dsc.isVisible()) {
+                return null;
+              }
 
-            String name = e.getExportName().substring(d + 1);
-            PrivateInternals_UiActionDescription.setMethod(
-                dsc,
-                e.getExportName().substring(0, d));
-            PrivateInternals_UiActionDescription.setId(
-                dsc,
-                "gerrit".equals(e.getPluginName())
-                  ? name
-                  : e.getPluginName() + '~' + name);
-            return dsc;
-          }
-        }),
-      Predicates.notNull());
+              String name = e.getExportName().substring(d + 1);
+              PrivateInternals_UiActionDescription.setMethod(
+                  dsc,
+                  e.getExportName().substring(0, d));
+              PrivateInternals_UiActionDescription.setId(
+                  dsc,
+                  "gerrit".equals(e.getPluginName())
+                    ? name
+                    : e.getPluginName() + '~' + name);
+              return dsc;
+            })
+        .filter(Objects::nonNull);
   }
 
   private UiActions() {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeBundle.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeBundle.java
index a8696a7..9228770 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeBundle.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeBundle.java
@@ -345,54 +345,36 @@
 
   private Map<PatchSetApproval.Key, PatchSetApproval>
       filterPatchSetApprovals() {
-    return limitToValidPatchSets(patchSetApprovals,
-        new Function<PatchSetApproval.Key, PatchSet.Id>() {
-          @Override
-          public PatchSet.Id apply(PatchSetApproval.Key in) {
-            return in.getParentKey();
-          }
-        });
+    return limitToValidPatchSets(
+        patchSetApprovals, PatchSetApproval.Key::getParentKey);
   }
 
   private Map<PatchLineComment.Key, PatchLineComment>
       filterPatchLineComments() {
-    return limitToValidPatchSets(patchLineComments,
-        new Function<PatchLineComment.Key, PatchSet.Id>() {
-          @Override
-          public PatchSet.Id apply(PatchLineComment.Key in) {
-            return in.getParentKey().getParentKey();
-          }
-        });
+    return limitToValidPatchSets(
+        patchLineComments,
+        k -> k.getParentKey().getParentKey());
   }
 
   private <K, V> Map<K, V> limitToValidPatchSets(Map<K, V> in,
-      final Function<K, PatchSet.Id> func) {
+      Function<K, PatchSet.Id> func) {
     return Maps.filterKeys(
         in, Predicates.compose(validPatchSetPredicate(), func));
   }
 
   private Predicate<PatchSet.Id> validPatchSetPredicate() {
-    final Predicate<PatchSet.Id> upToCurrent = upToCurrentPredicate();
-    return new Predicate<PatchSet.Id>() {
-      @Override
-      public boolean apply(PatchSet.Id in) {
-        return upToCurrent.apply(in) && patchSets.containsKey(in);
-      }
-    };
+    Predicate<PatchSet.Id> upToCurrent = upToCurrentPredicate();
+    return p -> upToCurrent.apply(p) && patchSets.containsKey(p);
   }
 
   private Collection<ChangeMessage> filterChangeMessages() {
     final Predicate<PatchSet.Id> validPatchSet = validPatchSetPredicate();
-    return Collections2.filter(changeMessages,
-        new Predicate<ChangeMessage>() {
-          @Override
-          public boolean apply(ChangeMessage in) {
-            PatchSet.Id psId = in.getPatchSetId();
-            if (psId == null) {
-              return true;
-            }
-            return validPatchSet.apply(psId);
+    return Collections2.filter(changeMessages, m -> {
+          PatchSet.Id psId = m.getPatchSetId();
+          if (psId == null) {
+            return true;
           }
+          return validPatchSet.apply(psId);
         });
   }
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java
index 42e4bc7..a5c4324 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java
@@ -19,9 +19,9 @@
 import static com.google.common.base.Preconditions.checkState;
 import static com.google.gerrit.reviewdb.client.RefNames.changeMetaRef;
 import static com.google.gerrit.server.notedb.NoteDbTable.CHANGES;
+import static java.util.Comparator.comparing;
 
 import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Function;
 import com.google.common.base.Predicate;
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.ImmutableList;
@@ -70,7 +70,6 @@
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
-import java.sql.Timestamp;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
@@ -84,22 +83,10 @@
   private static final Logger log = LoggerFactory.getLogger(ChangeNotes.class);
 
   static final Ordering<PatchSetApproval> PSA_BY_TIME =
-      Ordering.natural().onResultOf(
-        new Function<PatchSetApproval, Timestamp>() {
-          @Override
-          public Timestamp apply(PatchSetApproval input) {
-            return input.getGranted();
-          }
-        });
+      Ordering.from(comparing(PatchSetApproval::getGranted));
 
   public static final Ordering<ChangeMessage> MESSAGE_BY_TIME =
-      Ordering.natural().onResultOf(
-        new Function<ChangeMessage, Timestamp>() {
-          @Override
-          public Timestamp apply(ChangeMessage input) {
-            return input.getWrittenOn();
-          }
-        });
+      Ordering.from(comparing(ChangeMessage::getWrittenOn));
 
   public static ConfigInvalidException parseException(Change.Id changeId,
       String fmt, Object... args) {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesParser.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
index c001210..8bf8ca1 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
@@ -30,11 +30,10 @@
 import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_TOPIC;
 import static com.google.gerrit.server.notedb.NoteDbTable.CHANGES;
 import static java.util.Comparator.comparing;
+import static java.util.stream.Collectors.joining;
 
 import com.google.auto.value.AutoValue;
 import com.google.common.base.Enums;
-import com.google.common.base.Function;
-import com.google.common.base.Joiner;
 import com.google.common.base.Optional;
 import com.google.common.base.Splitter;
 import com.google.common.collect.ArrayListMultimap;
@@ -883,13 +882,8 @@
       missing.add(FOOTER_SUBJECT);
     }
     if (!missing.isEmpty()) {
-      throw parseException("Missing footers: " + Joiner.on(", ")
-          .join(Lists.transform(missing, new Function<FooterKey, String>() {
-            @Override
-            public String apply(FooterKey input) {
-              return input.getName();
-            }
-          })));
+      throw parseException("Missing footers: "
+          + missing.stream().map(FooterKey::getName).collect(joining(", ")));
     }
   }
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/RevisionNoteBuilder.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/RevisionNoteBuilder.java
index af463d7..be0a689 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/RevisionNoteBuilder.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/RevisionNoteBuilder.java
@@ -17,10 +17,9 @@
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.gerrit.server.PatchLineCommentsUtil.PLC_ORDER;
 import static java.nio.charset.StandardCharsets.UTF_8;
+import static java.util.stream.Collectors.toList;
 
-import com.google.common.base.Function;
 import com.google.common.collect.ArrayListMultimap;
-import com.google.common.collect.FluentIterable;
 import com.google.common.collect.Maps;
 import com.google.common.collect.Multimap;
 import com.google.gerrit.reviewdb.client.PatchLineComment;
@@ -134,13 +133,10 @@
     }
 
     RevisionNoteData data = new RevisionNoteData();
-    data.comments = FluentIterable.from(PLC_ORDER.sortedCopy(comments.values()))
-        .transform(new Function<PatchLineComment, RevisionNoteData.Comment>() {
-          @Override
-          public RevisionNoteData.Comment apply(PatchLineComment plc) {
-            return new RevisionNoteData.Comment(plc, noteUtil.getServerId());
-          }
-        }).toList();
+    data.comments = comments.values().stream()
+        .sorted(PLC_ORDER)
+        .map(plc -> new RevisionNoteData.Comment(plc, noteUtil.getServerId()))
+        .collect(toList());
     data.pushCert = pushCert;
 
     try (OutputStreamWriter osw = new OutputStreamWriter(out)) {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/RevisionNoteData.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/RevisionNoteData.java
index f4c7d8a..ce0831c 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/RevisionNoteData.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/RevisionNoteData.java
@@ -14,9 +14,9 @@
 
 package com.google.gerrit.server.notedb;
 
-import com.google.common.base.Function;
+import static java.util.stream.Collectors.toList;
+
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Lists;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Patch;
@@ -134,15 +134,15 @@
   List<Comment> comments;
 
   ImmutableList<PatchLineComment> exportComments(
-      final PatchLineComment.Status status) {
+      PatchLineComment.Status status) {
     return ImmutableList.copyOf(
-        Lists.transform(comments, new Function<Comment, PatchLineComment>() {
-          @Override
-          public PatchLineComment apply(Comment c) {
-            PatchLineComment plc = c.export();
-            plc.setStatus(status);
-            return plc;
-          }
-        }));
+        comments.stream()
+            .map(
+                c -> {
+                  PatchLineComment plc = c.export();
+                  plc.setStatus(status);
+                  return plc;
+                })
+            .collect(toList()));
   }
 }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/patch/PatchListLoader.java b/gerrit-server/src/main/java/com/google/gerrit/server/patch/PatchListLoader.java
index 2fa43bb..0ae9a99 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/patch/PatchListLoader.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/patch/PatchListLoader.java
@@ -16,12 +16,12 @@
 package com.google.gerrit.server.patch;
 
 import static com.google.common.base.Preconditions.checkArgument;
+
 import static java.nio.charset.StandardCharsets.UTF_8;
+import static java.util.stream.Collectors.toSet;
 import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
 
-import com.google.common.base.Function;
 import com.google.common.base.Throwables;
-import com.google.common.collect.FluentIterable;
 import com.google.gerrit.extensions.client.DiffPreferencesInfo.Whitespace;
 import com.google.gerrit.reviewdb.client.Patch;
 import com.google.gerrit.reviewdb.client.Project;
@@ -70,6 +70,7 @@
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
+import java.util.stream.Stream;
 
 public class PatchListLoader implements Callable<PatchList> {
   static final Logger log = LoggerFactory.getLogger(PatchListLoader.class);
@@ -179,16 +180,11 @@
             key.getNewId(), key.getWhitespace());
         PatchListKey oldKey = PatchListKey.againstDefaultBase(
             key.getOldId(), key.getWhitespace());
-        paths = FluentIterable
-            .from(patchListCache.get(newKey, project).getPatches())
-            .append(patchListCache.get(oldKey, project).getPatches())
-            .transform(new Function<PatchListEntry, String>() {
-              @Override
-              public String apply(PatchListEntry entry) {
-                return entry.getNewName();
-              }
-            })
-            .toSet();
+        paths = Stream.concat(
+                patchListCache.get(newKey, project).getPatches().stream(),
+                patchListCache.get(oldKey, project).getPatches().stream())
+            .map(PatchListEntry::getNewName)
+            .collect(toSet());
       }
 
       int cnt = diffEntries.size();
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/project/BanCommit.java b/gerrit-server/src/main/java/com/google/gerrit/server/project/BanCommit.java
index f0c2b78..ce97a83 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/project/BanCommit.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/project/BanCommit.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.server.project;
 
-import com.google.common.base.Function;
 import com.google.common.collect.Lists;
 import com.google.gerrit.common.errors.PermissionDeniedException;
 import com.google.gerrit.extensions.restapi.AuthException;
@@ -91,14 +90,7 @@
     if (commits == null || commits.isEmpty()) {
       return null;
     }
-
-    return Lists.transform(commits,
-        new Function<ObjectId, String>() {
-          @Override
-          public String apply(ObjectId id) {
-            return id.getName();
-          }
-        });
+    return Lists.transform(commits, ObjectId::getName);
   }
 
   public static class BanResultInfo {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/project/GetReflog.java b/gerrit-server/src/main/java/com/google/gerrit/server/project/GetReflog.java
index 1735c3d..8718a9b 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/project/GetReflog.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/project/GetReflog.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.server.project;
 
-import com.google.common.base.Function;
 import com.google.common.collect.Lists;
 import com.google.gerrit.extensions.common.GitPerson;
 import com.google.gerrit.extensions.restapi.AuthException;
@@ -102,12 +101,7 @@
           }
         }
       }
-      return Lists.transform(entries, new Function<ReflogEntry, ReflogEntryInfo>() {
-        @Override
-        public ReflogEntryInfo apply(ReflogEntry e) {
-          return new ReflogEntryInfo(e);
-        }
-      });
+      return Lists.transform(entries, ReflogEntryInfo::new);
     }
   }
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/project/ProjectState.java b/gerrit-server/src/main/java/com/google/gerrit/server/project/ProjectState.java
index 68d236e..bb6c62f 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/project/ProjectState.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/project/ProjectState.java
@@ -17,7 +17,6 @@
 import static com.google.gerrit.common.data.PermissionRule.Action.ALLOW;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
-import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
@@ -72,6 +71,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.function.Function;
 
 /** Cached information on a project. */
 public class ProjectState {
@@ -378,75 +378,35 @@
   }
 
   public boolean isUseContributorAgreements() {
-    return getInheritableBoolean(new Function<Project, InheritableBoolean>() {
-      @Override
-      public InheritableBoolean apply(Project input) {
-        return input.getUseContributorAgreements();
-      }
-    });
+    return getInheritableBoolean(Project::getUseContributorAgreements);
   }
 
   public boolean isUseContentMerge() {
-    return getInheritableBoolean(new Function<Project, InheritableBoolean>() {
-      @Override
-      public InheritableBoolean apply(Project input) {
-        return input.getUseContentMerge();
-      }
-    });
+    return getInheritableBoolean(Project::getUseContentMerge);
   }
 
   public boolean isUseSignedOffBy() {
-    return getInheritableBoolean(new Function<Project, InheritableBoolean>() {
-      @Override
-      public InheritableBoolean apply(Project input) {
-        return input.getUseSignedOffBy();
-      }
-    });
+    return getInheritableBoolean(Project::getUseSignedOffBy);
   }
 
   public boolean isRequireChangeID() {
-    return getInheritableBoolean(new Function<Project, InheritableBoolean>() {
-      @Override
-      public InheritableBoolean apply(Project input) {
-        return input.getRequireChangeID();
-      }
-    });
+    return getInheritableBoolean(Project::getRequireChangeID);
   }
 
   public boolean isCreateNewChangeForAllNotInTarget() {
-    return getInheritableBoolean(new Function<Project, InheritableBoolean>() {
-      @Override
-      public InheritableBoolean apply(Project input) {
-        return input.getCreateNewChangeForAllNotInTarget();
-      }
-    });
+    return getInheritableBoolean(Project::getCreateNewChangeForAllNotInTarget);
   }
 
   public boolean isEnableSignedPush() {
-    return getInheritableBoolean(new Function<Project, InheritableBoolean>() {
-      @Override
-      public InheritableBoolean apply(Project input) {
-        return input.getEnableSignedPush();
-      }
-    });
+    return getInheritableBoolean(Project::getEnableSignedPush);
   }
 
   public boolean isRequireSignedPush() {
-    return getInheritableBoolean(new Function<Project, InheritableBoolean>() {
-      @Override
-      public InheritableBoolean apply(Project input) {
-        return input.getRequireSignedPush();
-      }
-    });
+    return getInheritableBoolean(Project::getRequireSignedPush);
   }
 
   public boolean isRejectImplicitMerges() {
-    return getInheritableBoolean(new Function<Project, InheritableBoolean>() {
-      @Override
-      public InheritableBoolean apply(Project input) {
-        return input.getRejectImplicitMerges();
-      }
-    });
+    return getInheritableBoolean(Project::getRejectImplicitMerges);
   }
 
   public LabelTypes getLabelTypes() {
@@ -551,7 +511,8 @@
     return Files.exists(p) ? new String(Files.readAllBytes(p), UTF_8) : null;
   }
 
-  private boolean getInheritableBoolean(Function<Project, InheritableBoolean> func) {
+  private boolean getInheritableBoolean(
+      Function<Project, InheritableBoolean> func) {
     for (ProjectState s : tree()) {
       switch (func.apply(s.getProject())) {
         case TRUE:
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/AndSource.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/AndSource.java
index 168be5d..9f0bf89 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/AndSource.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/AndSource.java
@@ -16,7 +16,6 @@
 
 import static com.google.common.base.Preconditions.checkArgument;
 
-import com.google.common.base.Function;
 import com.google.common.base.Throwables;
 import com.google.common.collect.FluentIterable;
 import com.google.common.collect.ImmutableList;
@@ -157,12 +156,7 @@
 
   private Iterable<T> buffer(ResultSet<T> scanner) {
     return FluentIterable.from(Iterables.partition(scanner, 50))
-        .transformAndConcat(new Function<List<T>, List<T>>() {
-          @Override
-          public List<T> apply(List<T> buffer) {
-            return transformBuffer(buffer);
-          }
-        });
+        .transformAndConcat(this::transformBuffer);
   }
 
   protected List<T> transformBuffer(List<T> buffer) throws OrmRuntimeException {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/account/AccountQueryBuilder.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/account/AccountQueryBuilder.java
index 0288cb2..40fb3b6 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/account/AccountQueryBuilder.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/account/AccountQueryBuilder.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.server.query.account;
 
-import com.google.common.base.Function;
 import com.google.common.base.Splitter;
 import com.google.common.collect.Lists;
 import com.google.common.primitives.Ints;
@@ -124,13 +123,9 @@
 
   public Predicate<AccountState> defaultQuery(String query) {
     return Predicate.and(
-        Lists.transform(Splitter.on(' ').omitEmptyStrings().splitToList(query),
-            new Function<String, Predicate<AccountState>>() {
-              @Override
-              public Predicate<AccountState> apply(String s) {
-                return defaultField(s);
-              }
-            }));
+        Lists.transform(
+            Splitter.on(' ').omitEmptyStrings().splitToList(query),
+            this::defaultField));
   }
 
   @Override
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
index d7c7730..f697d15 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
@@ -16,9 +16,9 @@
 
 import static com.google.gerrit.reviewdb.client.Change.CHANGE_ID_PATTERN;
 import static com.google.gerrit.server.query.change.ChangeData.asChanges;
+import static java.util.stream.Collectors.toSet;
 
 import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Function;
 import com.google.common.base.Optional;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
@@ -26,7 +26,6 @@
 import com.google.common.primitives.Ints;
 import com.google.gerrit.common.data.GroupReference;
 import com.google.gerrit.common.errors.NotSignedInException;
-import com.google.gerrit.extensions.common.AccountInfo;
 import com.google.gerrit.extensions.registration.DynamicMap;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.AccountGroup;
@@ -632,14 +631,9 @@
     // expand a group predicate into multiple user predicates
     if (group != null) {
       Set<Account.Id> allMembers =
-          new HashSet<>(Lists.transform(
-              args.listMembers.get().setRecursive(true).apply(group),
-              new Function<AccountInfo, Account.Id>() {
-                @Override
-                public Account.Id apply(AccountInfo accountInfo) {
-                  return new Account.Id(accountInfo._accountId);
-                }
-              }));
+          args.listMembers.get().setRecursive(true).apply(group).stream()
+              .map(a -> new Account.Id(a._accountId))
+              .collect(toSet());
       int maxLimit = args.indexConfig.maxLimit();
       if (allMembers.size() > maxLimit) {
         // limit the number of query terms otherwise Gerrit will barf
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/InternalChangeQuery.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/InternalChangeQuery.java
index 5b1b1c6..daf8976 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/InternalChangeQuery.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/InternalChangeQuery.java
@@ -22,7 +22,6 @@
 import static com.google.gerrit.server.query.change.ChangeStatusPredicate.open;
 
 import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Function;
 import com.google.common.base.Strings;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Sets;
@@ -191,20 +190,14 @@
       }
     }
 
-    return Lists.transform(notesFactory.create(db, branch.getParentKey(),
-        changeIds, new com.google.common.base.Predicate<ChangeNotes>() {
-          @Override
-          public boolean apply(ChangeNotes notes) {
-            Change c = notes.getChange();
+    List<ChangeNotes> notes = notesFactory.create(
+        db, branch.getParentKey(), changeIds,
+        cn -> {
+            Change c = cn.getChange();
             return c.getDest().equals(branch)
                 && c.getStatus() != Change.Status.MERGED;
-          }
-        }), new Function<ChangeNotes, ChangeData>() {
-          @Override
-          public ChangeData apply(ChangeNotes notes) {
-            return changeDataFactory.create(db, notes);
-          }
         });
+    return Lists.transform(notes, n -> changeDataFactory.create(db, n));
   }
 
   private Iterable<ChangeData> byCommitsOnBranchNotMergedFromIndex(
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/schema/ProjectConfigSchemaUpdate.java b/gerrit-server/src/main/java/com/google/gerrit/server/schema/ProjectConfigSchemaUpdate.java
index 53ed5ac..2d9714f 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/schema/ProjectConfigSchemaUpdate.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/schema/ProjectConfigSchemaUpdate.java
@@ -15,9 +15,8 @@
 package com.google.gerrit.server.schema;
 
 import static com.google.gerrit.server.git.ProjectConfig.ACCESS;
+import static java.util.stream.Collectors.toList;
 
-import com.google.common.base.Function;
-import com.google.common.collect.Lists;
 import com.google.gerrit.common.data.PermissionRule;
 import com.google.gerrit.reviewdb.client.RefNames;
 import com.google.gerrit.server.git.MetaDataUpdate;
@@ -67,18 +66,16 @@
       Set<String> names = config.getNames(ACCESS, subsection);
       if (names.contains(name)) {
         List<String> values =
-            Arrays.asList(config.getStringList(ACCESS, subsection, name));
-        values = Lists.transform(values, new Function<String, String>() {
-          @Override
-          public String apply(String ruleString) {
-            PermissionRule rule = PermissionRule.fromString(ruleString, false);
-            if (rule.getForce()) {
-              rule.setForce(false);
-              updated = true;
-            }
-            return rule.asString(false);
-          }
-        });
+            Arrays.stream(config.getStringList(ACCESS, subsection, name))
+                .map(r -> {
+                      PermissionRule rule = PermissionRule.fromString(r, false);
+                      if (rule.getForce()) {
+                        rule.setForce(false);
+                        updated = true;
+                      }
+                      return rule.asString(false);
+                    })
+                .collect(toList());
         config.setStringList(ACCESS, subsection, name, values);
       }
     }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_124.java b/gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_124.java
index 16f0bcf..895c905 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_124.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_124.java
@@ -14,7 +14,8 @@
 
 package com.google.gerrit.server.schema;
 
-import com.google.common.base.Function;
+import static java.util.Comparator.comparing;
+
 import com.google.common.base.Strings;
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.Multimap;
@@ -124,13 +125,7 @@
 
   private Collection<AccountSshKey> fixInvalidSequenceNumbers(
       Collection<AccountSshKey> keys) {
-    Ordering<AccountSshKey> o =
-        Ordering.natural().onResultOf(new Function<AccountSshKey, Integer>() {
-          @Override
-          public Integer apply(AccountSshKey sshKey) {
-            return sshKey.getKey().get();
-          }
-        });
+    Ordering<AccountSshKey> o = Ordering.from(comparing(k -> k.getKey().get()));
     List<AccountSshKey> fixedKeys = new ArrayList<>(keys);
     AccountSshKey minKey = o.min(keys);
     while (minKey.getKey().get() <= 0) {
diff --git a/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java b/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java
index bd8259c..7a1dbf7 100644
--- a/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java
+++ b/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java
@@ -24,7 +24,6 @@
 import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
 import static org.junit.Assert.fail;
 
-import com.google.common.base.Function;
 import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableListMultimap;
@@ -34,7 +33,6 @@
 import com.google.common.collect.Iterables;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Lists;
-import com.google.common.collect.Ordering;
 import com.google.gerrit.common.TimeUtil;
 import com.google.gerrit.common.data.SubmitRecord;
 import com.google.gerrit.reviewdb.client.Account;
@@ -47,6 +45,7 @@
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.reviewdb.client.RevId;
+import com.google.gerrit.reviewdb.server.ReviewDbUtil;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.config.GerritServerId;
@@ -381,13 +380,9 @@
     update.commit();
 
     ChangeNotes notes = newNotes(c);
-    List<PatchSetApproval> approvals = Ordering.natural().onResultOf(
-        new Function<PatchSetApproval, Integer>() {
-          @Override
-          public Integer apply(PatchSetApproval in) {
-            return in.getAccountId().get();
-          }
-        }).sortedCopy(notes.getApprovals().get(c.currentPatchSetId()));
+    List<PatchSetApproval> approvals = ReviewDbUtil.intKeyOrdering()
+        .onResultOf(PatchSetApproval::getAccountId)
+        .sortedCopy(notes.getApprovals().get(c.currentPatchSetId()));
     assertThat(approvals).hasSize(2);
 
     assertThat(approvals.get(0).getAccountId())
diff --git a/gerrit-server/src/test/java/com/google/gerrit/server/query/account/AbstractQueryAccountsTest.java b/gerrit-server/src/test/java/com/google/gerrit/server/query/account/AbstractQueryAccountsTest.java
index f7b3b11..b65d49d 100644
--- a/gerrit-server/src/test/java/com/google/gerrit/server/query/account/AbstractQueryAccountsTest.java
+++ b/gerrit-server/src/test/java/com/google/gerrit/server/query/account/AbstractQueryAccountsTest.java
@@ -17,7 +17,6 @@
 import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.fail;
 
-import com.google.common.base.Function;
 import com.google.common.collect.FluentIterable;
 import com.google.common.collect.ImmutableList;
 import com.google.gerrit.extensions.api.GerritApi;
@@ -476,22 +475,10 @@
   }
 
   protected static Iterable<Integer> ids(AccountInfo... accounts) {
-    return FluentIterable.from(Arrays.asList(accounts)).transform(
-        new Function<AccountInfo, Integer>() {
-          @Override
-          public Integer apply(AccountInfo in) {
-            return in._accountId;
-          }
-        });
+    return FluentIterable.of(accounts).transform(a -> a._accountId);
   }
 
   protected static Iterable<Integer> ids(Iterable<AccountInfo> accounts) {
-    return FluentIterable.from(accounts).transform(
-        new Function<AccountInfo, Integer>() {
-          @Override
-          public Integer apply(AccountInfo in) {
-            return in._accountId;
-          }
-        });
+    return FluentIterable.from(accounts).transform(a -> a._accountId);
   }
 }