Replace Collections.emptyXXX with Immutable Static Factory Methods

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

@@ -0,0 +1,60 @@
+/*
+ * 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.JavaTemplate;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.search.UsesJavaVersion;
+import org.openrewrite.java.search.UsesMethod;
+import org.openrewrite.java.tree.J;
+
+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 TreeVisitor<?, ExecutionContext> getVisitor() {
+        TreeVisitor<?, ExecutionContext> check = Preconditions.and(new UsesJavaVersion<>(9),
+                new UsesMethod<>(EMPTY_LIST));
+        return Preconditions.check(check, 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");
+                    return JavaTemplate.builder("List.of()")
+                            .contextSensitive()
+                            .imports("java.util.List")
+                            .build()
+                            .apply(updateCursor(m), m.getCoordinates().replace());
+                }
+
+                return m;
+            }
+        });
+    }
+}

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

@@ -0,0 +1,60 @@
+/*
+ * 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.JavaTemplate;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.search.UsesJavaVersion;
+import org.openrewrite.java.search.UsesMethod;
+import org.openrewrite.java.tree.J;
+
+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 TreeVisitor<?, ExecutionContext> getVisitor() {
+        TreeVisitor<?, ExecutionContext> check = Preconditions.and(new UsesJavaVersion<>(9),
+                new UsesMethod<>(EMPTY_MAP));
+        return Preconditions.check(check, 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");
+                    return JavaTemplate.builder("Map.of()")
+                            .contextSensitive()
+                            .imports("java.util.Map")
+                            .build()
+                            .apply(updateCursor(m), m.getCoordinates().replace());
+                }
+
+                return m;
+            }
+        });
+    }
+}

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

@@ -0,0 +1,60 @@
+/*
+ * 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.JavaTemplate;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.search.UsesJavaVersion;
+import org.openrewrite.java.search.UsesMethod;
+import org.openrewrite.java.tree.J;
+
+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 TreeVisitor<?, ExecutionContext> getVisitor() {
+        TreeVisitor<?, ExecutionContext> check = Preconditions.and(new UsesJavaVersion<>(9),
+                new UsesMethod<>(EMPTY_SET));
+        return Preconditions.check(check, 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");
+                    return JavaTemplate.builder("Set.of()")
+                            .contextSensitive()
+                            .imports("java.util.Set")
+                            .build()
+                            .apply(updateCursor(m), m.getCoordinates().replace());
+                }
+
+                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-best-practices.yml

@@ -48,10 +48,7 @@ recipeList:
   - org.openrewrite.java.migrate.lang.var.UseVarForGenericMethodInvocations
   - org.openrewrite.java.migrate.lang.var.UseVarForPrimitive
   # Prefer modern Java collection factories and utilities
-  - org.openrewrite.java.migrate.util.UseEnumSetOf
-  - org.openrewrite.java.migrate.util.UseListOf
-  - org.openrewrite.java.migrate.util.UseMapOf
-  - org.openrewrite.java.migrate.util.UseSetOf
+  - org.openrewrite.java.migrate.util.JavaUtilAPIs
   # Static analysis: bug prevention
   - org.openrewrite.staticanalysis.ReplaceWeekYearWithYear
   - org.openrewrite.staticanalysis.RemoveHashCodeCallsFromArrayInstances

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

@@ -22,10 +22,26 @@ description: Certain java util APIs have been introduced and are favored over pr
 preconditions:
   - org.openrewrite.Singleton
 recipeList:
+  - org.openrewrite.java.migrate.util.IteratorNext
+  - org.openrewrite.java.migrate.util.ListFirstAndLast
+  - 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
   - org.openrewrite.java.migrate.util.MigrateCollectionsUnmodifiableList
   - org.openrewrite.java.migrate.util.MigrateCollectionsUnmodifiableSet
+  - org.openrewrite.java.migrate.util.MigrateStringReaderToReaderOf
+  - org.openrewrite.java.migrate.util.OptionalNotEmptyToIsPresent
+  - org.openrewrite.java.migrate.util.OptionalNotPresentToIsEmpty
+  - org.openrewrite.java.migrate.util.OptionalStreamRecipe
+  - org.openrewrite.java.migrate.util.RemoveFinalizerFromZip
+  - org.openrewrite.java.migrate.util.ReplaceMathRandomWithThreadLocalRandomRecipe
   - org.openrewrite.java.migrate.util.ReplaceStreamCollectWithToList
+  - org.openrewrite.java.migrate.util.StreamFindFirst
+  - org.openrewrite.java.migrate.util.UseEnumSetOf
+  - org.openrewrite.java.migrate.util.UseListOf
+  - org.openrewrite.java.migrate.util.UseLocaleOf
   - org.openrewrite.java.migrate.util.UseMapOf
+  - org.openrewrite.java.migrate.util.UseSetOf