Issue: checkstyle#48: Created new Recipe for Redundant Import

Author: Anmol202005

src/main/java/org/checkstyle/autofix/CheckstyleCheck.java

@@ -21,9 +21,10 @@
 import java.util.Optional;
 
 public enum CheckstyleCheck {
-    UPPERELL("com.puppycrawl.tools.checkstyle.checks.UpperEllCheck"),
+    FINALLOCALVARIABLE("com.puppycrawl.tools.checkstyle.checks.coding.FinalLocalVariableCheck"),
     HEADER("com.puppycrawl.tools.checkstyle.checks.header.HeaderCheck"),
-    FINALLOCALVARIABLE("com.puppycrawl.tools.checkstyle.checks.coding.FinalLocalVariableCheck");
+    REDUNDANTIMPORT("com.puppycrawl.tools.checkstyle.checks.imports.RedundantImportCheck"),
+    UPPERELL("com.puppycrawl.tools.checkstyle.checks.UpperEllCheck");
 
     private final String id;
 

src/main/java/org/checkstyle/autofix/CheckstyleRecipeRegistry.java

@@ -30,6 +30,7 @@
 import org.checkstyle.autofix.parser.CheckstyleViolation;
 import org.checkstyle.autofix.recipe.FinalLocalVariable;
 import org.checkstyle.autofix.recipe.Header;
+import org.checkstyle.autofix.recipe.RedundantImport;
 import org.checkstyle.autofix.recipe.UpperEll;
 import org.openrewrite.Recipe;
 
@@ -45,6 +46,7 @@ public final class CheckstyleRecipeRegistry {
     static {
         RECIPE_MAP.put(CheckstyleCheck.UPPERELL, UpperEll::new);
         RECIPE_MAP.put(CheckstyleCheck.FINALLOCALVARIABLE, FinalLocalVariable::new);
+        RECIPE_MAP.put(CheckstyleCheck.REDUNDANTIMPORT, RedundantImport::new);
         RECIPE_MAP_WITH_CONFIG.put(CheckstyleCheck.HEADER, Header::new);
     }
 

src/main/java/org/checkstyle/autofix/recipe/RedundantImport.java

@@ -0,0 +1,126 @@
+///////////////////////////////////////////////////////////////////////////////////////////////
+// checkstyle-openrewrite-recipes: Automatically fix Checkstyle violations with OpenRewrite.
+// Copyright (C) 2025 The Checkstyle OpenRewrite Recipes Authors
+//
+// 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
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// 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.checkstyle.autofix.recipe;
+
+import java.nio.file.Path;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.checkstyle.autofix.PositionHelper;
+import org.checkstyle.autofix.parser.CheckstyleViolation;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Recipe;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.tree.J;
+
+public class RedundantImport extends Recipe {
+
+    private static final String JAVA_LANG_PREFIX = "java.lang.";
+
+    private final List<CheckstyleViolation> violations;
+
+    public RedundantImport(List<CheckstyleViolation> violations) {
+        this.violations = violations;
+    }
+
+    @Override
+    public String getDisplayName() {
+        return "Remove redundant imports";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Remove duplicate imports, java.lang imports, and same package imports";
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return new RemoveRedundantImportsVisitor();
+    }
+
+    private final class RemoveRedundantImportsVisitor extends JavaIsoVisitor<ExecutionContext> {
+
+        private Path sourcePath;
+
+        @Override
+        public J.CompilationUnit visitCompilationUnit(J.CompilationUnit cu, ExecutionContext ctx) {
+
+            this.sourcePath = cu.getSourcePath().toAbsolutePath();
+
+            final Set<String> seenImports = new HashSet<>();
+            final String currentPackage = getCurrentPackage(cu);
+
+            return cu.withImports(
+                    cu.getImports().stream()
+                            .filter(importStmt -> {
+                                return !isRedundant(importStmt, seenImports,
+                                    currentPackage) || !isAtViolationLocation(importStmt); })
+                            .toList()
+            );
+        }
+
+        private boolean isRedundant(J.Import importStmt,
+                                    Set<String> seenImports, String currentPackage) {
+            final String importName = importStmt.getQualid().toString();
+
+            boolean isRedundant = false;
+
+            if (seenImports.contains(importName)) {
+                isRedundant = true;
+            }
+            else {
+                seenImports.add(importName);
+
+                if (!importStmt.isStatic() && importName.startsWith(JAVA_LANG_PREFIX)) {
+                    isRedundant = true;
+                }
+                else if (currentPackage != null && !importStmt.isStatic()
+                        && importName.startsWith(currentPackage + ".")) {
+                    isRedundant = true;
+                }
+            }
+
+            return isRedundant;
+        }
+
+        private String getCurrentPackage(J.CompilationUnit compilationUnit) {
+            String currentPackage = null;
+            if (compilationUnit.getPackageDeclaration() != null) {
+                currentPackage = compilationUnit.getPackageDeclaration()
+                        .getExpression().printTrimmed(getCursor());
+            }
+            return currentPackage;
+        }
+
+        private boolean isAtViolationLocation(J.Import literal) {
+            final J.CompilationUnit cursor = getCursor().firstEnclosing(J.CompilationUnit.class);
+
+            final int line = PositionHelper.computeLinePosition(cursor, literal, getCursor());
+            final int column = PositionHelper.computeColumnPosition(cursor, literal, getCursor());
+            return violations.removeIf(violation -> {
+                final Path absolutePath = Path.of(violation.getFileName()).toAbsolutePath();
+                return violation.getLine() == line
+                        && violation.getColumn() == column
+                        && absolutePath.equals(sourcePath);
+            });
+        }
+
+    }
+}

src/test/java/org/checkstyle/autofix/recipe/RedundantImportTest.java

@@ -0,0 +1,39 @@
+///////////////////////////////////////////////////////////////////////////////////////////////
+// checkstyle-openrewrite-recipes: Automatically fix Checkstyle violations with OpenRewrite.
+// Copyright (C) 2025 The Checkstyle OpenRewrite Recipes Authors
+//
+// 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
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// 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.checkstyle.autofix.recipe;
+
+import org.junit.jupiter.api.Test;
+
+public class RedundantImportTest extends AbstractRecipeTestSupport {
+
+    @Override
+    protected String getSubpackage() {
+        return "redundantimport";
+    }
+
+    @Test
+    void duplicateImport() throws Exception {
+        verify("DuplicateImport");
+    }
+
+    @Test
+    void complexCase() throws Exception {
+        verify("ComplexCase");
+    }
+
+}

src/test/resources/org/checkstyle/autofix/recipe/redundantimport/complexcase/InputComplexCase.java

@@ -0,0 +1,46 @@
+/*xml
+<module name="Checker">
+  <module name="TreeWalker">
+    <module name="com.puppycrawl.tools.checkstyle.checks.imports.RedundantImportCheck"/>
+  </module>
+</module>
+
+*/
+
+package org.checkstyle.autofix.recipe.redundantimport.complexcase;
+
+import org.checkstyle.autofix.recipe.redundantimport.complexcase.*; // violation 'Redundant import from the same package'
+import java.io.*;
+    import java.lang.*; // violation 'Redundant import from the java.lang package'
+
+import java.util.List;
+import java.util.List; // violation 'Duplicate import'
+import java.util.Iterator;
+import java.util.Enumeration;
+import java.util.Arrays;
+
+import javax.swing.JToolBar;
+import javax.swing.JToggleButton;
+import javax.swing.ScrollPaneLayout;
+import javax.swing.BorderFactory;
+
+import static java.io.File.listRoots;
+import static javax.swing.WindowConstants.*;
+import static javax.swing.WindowConstants.*; // violation 'Duplicate import'
+import static java.io.File.createTempFile;
+import static java.io.File.pathSeparator;
+import static org.checkstyle.autofix.recipe.redundantimport.complexcase.InputComplexCase.myStaticMethod;
+
+import java.awt.Component;
+import java.awt.Graphics2D;
+import java.awt.HeadlessException;
+import java.awt.Label;
+import java.util.Date;
+import java.util.Calendar;
+import java.util.BitSet;
+
+import static java.lang.Math.PI;
+
+class InputComplexCase {
+    public static void myStaticMethod() {}
+}

src/test/resources/org/checkstyle/autofix/recipe/redundantimport/complexcase/OutputComplexCase.java

@@ -0,0 +1,41 @@
+/*xml
+<module name="Checker">
+  <module name="TreeWalker">
+    <module name="com.puppycrawl.tools.checkstyle.checks.imports.RedundantImportCheck"/>
+  </module>
+</module>
+
+*/
+
+package org.checkstyle.autofix.recipe.redundantimport.complexcase;
+import java.io.*;
+
+import java.util.List;
+import java.util.Iterator;
+import java.util.Enumeration;
+import java.util.Arrays;
+
+import javax.swing.JToolBar;
+import javax.swing.JToggleButton;
+import javax.swing.ScrollPaneLayout;
+import javax.swing.BorderFactory;
+
+import static java.io.File.listRoots;
+import static javax.swing.WindowConstants.*;
+import static java.io.File.createTempFile;
+import static java.io.File.pathSeparator;
+import static org.checkstyle.autofix.recipe.redundantimport.complexcase.InputComplexCase.myStaticMethod;
+
+import java.awt.Component;
+import java.awt.Graphics2D;
+import java.awt.HeadlessException;
+import java.awt.Label;
+import java.util.Date;
+import java.util.Calendar;
+import java.util.BitSet;
+
+import static java.lang.Math.PI;
+
+class OutputComplexCase {
+    public static void myStaticMethod() {}
+}

src/test/resources/org/checkstyle/autofix/recipe/redundantimport/duplicateimport/InputDuplicateImport.java

@@ -0,0 +1,19 @@
+/*xml
+<module name="Checker">
+  <module name="TreeWalker">
+    <module name="com.puppycrawl.tools.checkstyle.checks.imports.RedundantImportCheck"/>
+  </module>
+</module>
+
+*/
+
+package org.checkstyle.autofix.recipe.redundantimport.duplicateimport;
+
+import static java.util.Arrays.asList;
+import static java.util.Arrays.asList; // violation 'Duplicate import'
+
+import java.util.List;
+import java.util.List; // violation 'Duplicate import'
+import java.util.Set;
+
+public class InputDuplicateImport {}

src/test/resources/org/checkstyle/autofix/recipe/redundantimport/duplicateimport/OutputDuplicateImport.java

@@ -0,0 +1,17 @@
+/*xml
+<module name="Checker">
+  <module name="TreeWalker">
+    <module name="com.puppycrawl.tools.checkstyle.checks.imports.RedundantImportCheck"/>
+  </module>
+</module>
+
+*/
+
+package org.checkstyle.autofix.recipe.redundantimport.duplicateimport;
+
+import static java.util.Arrays.asList;
+
+import java.util.List;
+import java.util.Set;
+
+public class OutputDuplicateImport {}