Replace Collections.emptyXXX with Immutable Static Factory Methods

src/main/java/org/openrewrite/java/migrate/util/MigrateCollectionsEmptyList.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2026 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://docs.moderne.io/licensing/moderne-source-available-license
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.migrate.util;
+
+import lombok.Getter;
+import org.openrewrite.*;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaType;
+import org.openrewrite.java.tree.JavaType.ShallowClass;
+import org.openrewrite.java.tree.Space;
+
+import static java.util.Collections.emptyList;
+
+public class MigrateCollectionsEmptyList extends Recipe {
+    private static final MethodMatcher EMPTY_LIST = new MethodMatcher("java.util.Collections emptyList()");
+
+    @Getter
+    final String displayName = "Prefer `List.of()`";
+
+    @Getter
+    final String description = "Prefer `List.of()` instead of using `Collections.emptyList()` in Java 9 or higher.";
+
+    @Override
+    public JavaIsoVisitor<ExecutionContext> getVisitor() {
+        return new JavaIsoVisitor<ExecutionContext>() {
+
+            @Override
+            public J.MethodInvocation visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx) {
+                J.MethodInvocation m = super.visitMethodInvocation(method, ctx);
+
+                if (EMPTY_LIST.matches(m)) {
+                    maybeRemoveImport("java.util.Collections");
+                    maybeAddImport("java.util.List");
+
+                    JavaType.Class classType = ShallowClass.build("java.util.List");
+                    JavaType.Method methodType = m.getMethodType().withName("of").withDeclaringType(classType);
+                    m = m.withName(m.getName().withSimpleName("of").withType(methodType));
+                    if (m.getSelect() instanceof J.Identifier) {
+                        return m.withSelect(((J.Identifier) m.getSelect()).withSimpleName("List").withType(classType));
+                    }
+                    return m.withSelect(new J.Identifier(
+                                    Tree.randomId(), m.getPrefix(), m.getMarkers(), emptyList(), "List", classType, null))
+                            .withPrefix(Space.EMPTY);
+                }
+
+                return m;
+            }
+        };
+    }
+}

src/main/java/org/openrewrite/java/migrate/util/MigrateCollectionsEmptyMap.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2026 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://docs.moderne.io/licensing/moderne-source-available-license
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.migrate.util;
+
+import lombok.Getter;
+import org.openrewrite.*;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaType;
+import org.openrewrite.java.tree.JavaType.ShallowClass;
+import org.openrewrite.java.tree.Space;
+
+import static java.util.Collections.emptyList;
+
+public class MigrateCollectionsEmptyMap extends Recipe {
+    private static final MethodMatcher EMPTY_MAP = new MethodMatcher("java.util.Collections emptyMap()");
+
+    @Getter
+    final String displayName = "Prefer `Map.of()`";
+
+    @Getter
+    final String description = "Prefer `Map.of()` instead of using `Collections.emptyMap()` in Java 9 or higher.";
+
+    @Override
+    public JavaIsoVisitor<ExecutionContext> getVisitor() {
+        return new JavaIsoVisitor<ExecutionContext>() {
+
+            @Override
+            public J.MethodInvocation visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx) {
+                J.MethodInvocation m = super.visitMethodInvocation(method, ctx);
+
+                if (EMPTY_MAP.matches(m)) {
+                    maybeRemoveImport("java.util.Collections");
+                    maybeAddImport("java.util.Map");
+
+                    JavaType.Class classType = ShallowClass.build("java.util.Map");
+                    JavaType.Method methodType = m.getMethodType().withName("of").withDeclaringType(classType);
+                    m = m.withName(m.getName().withSimpleName("of").withType(methodType));
+                    if (m.getSelect() instanceof J.Identifier) {
+                        return m.withSelect(((J.Identifier) m.getSelect()).withSimpleName("Map").withType(classType));
+                    }
+                    return m.withSelect(new J.Identifier(
+                                    Tree.randomId(), m.getPrefix(), m.getMarkers(), emptyList(), "Map", classType, null))
+                            .withPrefix(Space.EMPTY);
+                }
+
+                return m;
+            }
+        };
+    }
+}

src/main/java/org/openrewrite/java/migrate/util/MigrateCollectionsEmptySet.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2026 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://docs.moderne.io/licensing/moderne-source-available-license
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.migrate.util;
+
+import lombok.Getter;
+import org.openrewrite.*;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaType;
+import org.openrewrite.java.tree.JavaType.ShallowClass;
+import org.openrewrite.java.tree.Space;
+
+import static java.util.Collections.emptyList;
+
+public class MigrateCollectionsEmptySet extends Recipe {
+    private static final MethodMatcher EMPTY_SET = new MethodMatcher("java.util.Collections emptySet()");
+
+    @Getter
+    final String displayName = "Prefer `Set.of()`";
+
+    @Getter
+    final String description = "Prefer `Set.of()` instead of using `Collections.emptySet()` in Java 9 or higher.";
+
+    @Override
+    public JavaIsoVisitor<ExecutionContext> getVisitor() {
+        return new JavaIsoVisitor<ExecutionContext>() {
+
+            @Override
+            public J.MethodInvocation visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx) {
+                J.MethodInvocation m = super.visitMethodInvocation(method, ctx);
+
+                if (EMPTY_SET.matches(m)) {
+                    maybeRemoveImport("java.util.Collections");
+                    maybeAddImport("java.util.Set");
+
+                    JavaType.Class classType = ShallowClass.build("java.util.Set");
+                    JavaType.Method methodType = m.getMethodType().withName("of").withDeclaringType(classType);
+                    m = m.withName(m.getName().withSimpleName("of").withType(methodType));
+                    if (m.getSelect() instanceof J.Identifier) {
+                        return m.withSelect(((J.Identifier) m.getSelect()).withSimpleName("Set").withType(classType));
+                    }
+                    return m.withSelect(new J.Identifier(
+                                    Tree.randomId(), m.getPrefix(), m.getMarkers(), emptyList(), "Set", classType, null))
+                            .withPrefix(Space.EMPTY);
+                }
+
+                return m;
+            }
+        };
+    }
+}

src/main/resources/META-INF/rewrite/examples.yml

@@ -8809,6 +8809,63 @@ examples:
     language: java
 ---
 type: specs.openrewrite.org/v1beta/example
+recipeName: org.openrewrite.java.migrate.util.MigrateCollectionsEmptyList
+examples:
+- description: '`MigrateCollectionsEmptyListTest#emptyList`'
+  sources:
+  - before: |
+      import java.util.*;
+
+      class Test {
+          List<String> list = Collections.emptyList();
+      }
+    after: |
+      import java.util.List;
+
+      class Test {
+          List<String> list = List.of();
+      }
+    language: java
+---
+type: specs.openrewrite.org/v1beta/example
+recipeName: org.openrewrite.java.migrate.util.MigrateCollectionsEmptySet
+examples:
+- description: '`MigrateCollectionsEmptySetTest#emptySet`'
+  sources:
+  - before: |
+      import java.util.*;
+
+      class Test {
+          Set<String> set = Collections.emptySet();
+      }
+    after: |
+      import java.util.Set;
+
+      class Test {
+          Set<String> set = Set.of();
+      }
+    language: java
+---
+type: specs.openrewrite.org/v1beta/example
+recipeName: org.openrewrite.java.migrate.util.MigrateCollectionsEmptyMap
+examples:
+- description: '`MigrateCollectionsEmptyMapTest#emptyMap`'
+  sources:
+  - before: |
+      import java.util.*;
+
+      class Test {
+          Map<String, String> map = Collections.emptyMap();
+      }
+    after: |
+      import java.util.Map;
+
+      class Test {
+          Map<String, String> map = Map.of();
+      }
+    language: java
+---
+type: specs.openrewrite.org/v1beta/example
 recipeName: org.openrewrite.java.migrate.util.MigrateCollectionsSingletonList
 examples:
 - description: '`MigrateCollectionsSingletonListTest#singletonList`'

src/main/resources/META-INF/rewrite/java-util-apis.yml

@@ -22,6 +22,9 @@ description: Certain java util APIs have been introduced and are favored over pr
 preconditions:
   - org.openrewrite.Singleton
 recipeList:
+  - org.openrewrite.java.migrate.util.MigrateCollectionsEmptyList
+  - org.openrewrite.java.migrate.util.MigrateCollectionsEmptyMap
+  - org.openrewrite.java.migrate.util.MigrateCollectionsEmptySet
   - org.openrewrite.java.migrate.util.MigrateCollectionsSingletonList
   - org.openrewrite.java.migrate.util.MigrateCollectionsSingletonMap
   - org.openrewrite.java.migrate.util.MigrateCollectionsSingletonSet