UseMapOf

Author: jkschneider

src/main/java/org/openrewrite/java/migrate/lang/UseMapOf.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2021 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (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://www.apache.org/licenses/LICENSE-2.0
+ * <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.lang;
+
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Recipe;
+import org.openrewrite.java.JavaTemplate;
+import org.openrewrite.java.JavaVisitor;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.tree.Expression;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.Statement;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.StringJoiner;
+
+public class UseMapOf extends Recipe {
+    private static final MethodMatcher NEW_HASH_MAP = new MethodMatcher("java.util.HashMap <constructor>()", true);
+    private static final MethodMatcher MAP_PUT = new MethodMatcher("java.util.Map put(..)", true);
+
+    @Override
+    public String getDisplayName() {
+        return "Use `Map.of(..)` where possible";
+    }
+
+    @Override
+    public String getDescription() {
+        return "This succinct syntax was introduced in Java 10.";
+    }
+
+    @Override
+    protected JavaVisitor<ExecutionContext> getVisitor() {
+        return new JavaVisitor<ExecutionContext>() {
+            @Override
+            public J visitNewClass(J.NewClass newClass, ExecutionContext ctx) {
+                J.NewClass n = (J.NewClass) super.visitNewClass(newClass, ctx);
+                J.Block body = n.getBody();
+                if (NEW_HASH_MAP.matches(n) && body != null) {
+                    if (body.getStatements().size() == 1) {
+                        Statement statement = body.getStatements().get(0);
+                        if (statement instanceof J.Block) {
+                            List<Expression> args = new ArrayList<>();
+                            StringJoiner mapOf = new StringJoiner(", ", "Map.of(", ")");
+                            for (Statement stat : ((J.Block) statement).getStatements()) {
+                                if (stat instanceof J.MethodInvocation && MAP_PUT.matches((Expression) stat)) {
+                                    J.MethodInvocation put = (J.MethodInvocation) stat;
+                                    args.addAll(put.getArguments());
+                                    mapOf.add("#{}");
+                                    mapOf.add("#{}");
+                                } else {
+                                    return n;
+                                }
+                            }
+
+                            maybeRemoveImport("java.util.HashMap");
+                            maybeAddImport("java.util.Map");
+                            return autoFormat(n.withTemplate(
+                                    JavaTemplate
+                                            .builder(this::getCursor, mapOf.toString())
+                                            .imports("java.util.Map")
+                                            .build(),
+                                    n.getCoordinates().replace(),
+                                    args.toArray()
+                            ), ctx);
+                        }
+                    }
+                }
+                return n;
+            }
+        };
+    }
+}

src/test/kotlin/org/openrewrite/java/migrate/lang/UseMapOfTest.kt

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2021 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (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://www.apache.org/licenses/LICENSE-2.0
+ * <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.lang
+
+import org.junit.jupiter.api.Test
+import org.openrewrite.Recipe
+import org.openrewrite.java.JavaRecipeTest
+
+class UseMapOfTest: JavaRecipeTest {
+    override val recipe: Recipe
+        get() = UseMapOf()
+
+    @Test
+    fun anonymousClass() = assertChanged(
+        before = """
+            import java.util.HashMap;
+            import java.util.Map;
+            
+            class Test {
+                Map<String, String> m = new HashMap<>() {{
+                    put("stru", "menta");
+                    put("mod", "erne");
+                }};
+            }
+        """,
+        after = """
+            import java.util.Map;
+            
+            class Test {
+                Map<String, String> m = Map.of("stru", "menta", "mod", "erne");
+            }
+        """
+    )
+}