Unnecessary return as last statement in void method

src/main/java/org/openrewrite/staticanalysis/UnnecessaryReturnAsLastStatement.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2024 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.staticanalysis;
+
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Recipe;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.Statement;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class UnnecessaryReturnAsLastStatement extends Recipe {
+    @Override
+    public String getDisplayName() {
+        return "Unnecessary `return` as last statement in void method";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Removes `return` from a `void` method if it's the last statement.";
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return new JavaIsoVisitor<ExecutionContext>() {
+            private Statement maybeRemoveReturnAsLastStatement(Statement s) {
+                if (s instanceof J.Block) {
+                    return maybeRemoveReturnAsLastStatement((J.Block) s);
+                } else {
+                    return s;
+                }
+            }
+
+            private J.Block maybeRemoveReturnAsLastStatement(J.Block b) {
+                if (b == null) {
+                    return null;
+                }
+
+                List<Statement> statements = b.getStatements();
+                if (statements.isEmpty()) {
+                    return b;
+                }
+                Statement lastStatement = statements.get(statements.size() - 1);
+                List<Statement> allButLast = statements.subList(0, statements.size() - 1);
+                if (lastStatement instanceof J.Return) {
+                    return b.withStatements(allButLast);
+                } else if (lastStatement instanceof J.If) {
+                    J.If ifStatement = (J.If) lastStatement;
+                    J.If.Else elze = ifStatement.getElsePart();
+                    J.If newIf = ifStatement
+                            .withThenPart(maybeRemoveReturnAsLastStatement(ifStatement.getThenPart()))
+                            .withElsePart(elze.withBody(maybeRemoveReturnAsLastStatement(elze.getBody())));
+                    List<Statement> newStatements = new ArrayList<>(allButLast);
+                    newStatements.add(newIf);
+                    return b.withStatements(newStatements);
+                } else {
+                    return b;
+                }
+            }
+
+            @Override
+            public J.MethodDeclaration visitMethodDeclaration(J.MethodDeclaration method, ExecutionContext ctx) {
+                J.MethodDeclaration m = super.visitMethodDeclaration(method, ctx);
+                if (m == null) {
+                    return m;
+                }
+                return m.withBody(maybeRemoveReturnAsLastStatement(m.getBody()));
+            }
+        };
+    }
+}

src/test/java/org/openrewrite/staticanalysis/UnnecessaryReturnAsLastStatementTest.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright 2024 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.staticanalysis;
+
+import org.junit.jupiter.api.Test;
+import org.openrewrite.DocumentExample;
+import org.openrewrite.test.RecipeSpec;
+import org.openrewrite.test.RewriteTest;
+
+import static org.openrewrite.java.Assertions.java;
+
+class UnnecessaryReturnAsLastStatementTest implements RewriteTest {
+    @Override
+    public void defaults(RecipeSpec spec) {
+        spec.recipe(new UnnecessaryReturnAsLastStatement());
+    }
+
+    @Test
+    @DocumentExample
+    void simpleReturn() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              class Hello {
+                  void world() {
+                      System.out.println("Hello world");
+                      return;
+                  }
+              }
+              """,
+            """
+              class Hello {
+                  void world() {
+                      System.out.println("Hello world");
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void ifBranches() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              class Hello {
+                  void world(int i) {
+                      if (i > 0) {
+                        System.out.println("Positive");
+                        return;
+                      } else {
+                        System.out.println("Zero or negative");
+                        return;
+                      }
+                  }
+              }
+              """,
+            """
+              class Hello {
+                  void world(int i) {
+                      if (i > 0) {
+                        System.out.println("Positive");
+                      } else {
+                        System.out.println("Zero or negative");
+                      }
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void ifIsNotTheLast() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              class Hello {
+                  void world(int i) {
+                      if (i > 0) {
+                        System.out.println("Positive");
+                        return;
+                      } else {
+                        System.out.println("Zero or negative");
+                      }
+                      System.out.println("Some extra logic");
+                  }
+              }
+              """));
+    }
+}