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Add RemovePrivateFieldUnderscores recipe
This recipe removes prefix or suffix underscores from private class field names. This helps enforce modern Java coding standards. For clarity and consistency, the recipe also adds a qualifier to all updated field accesses. This prevents ambiguity with local variables and ensures a uniform style throughout the class. Fixes #630
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‎src/main/java/org/openrewrite/staticanalysis/RemovePrivateFieldUnderscores.java‎

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/*
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* Copyright 2025 the original author or authors.
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* <p>
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* Licensed under the Moderne Source Available License (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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* <p>
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* https://docs.moderne.io/licensing/moderne-source-available-license
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* <p>
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.openrewrite.staticanalysis;
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import org.openrewrite.*;
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import org.openrewrite.java.*;
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import org.openrewrite.java.tree.*;
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import org.openrewrite.marker.Markers;
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import static java.util.Collections.emptyList;
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public class RemovePrivateFieldUnderscores extends Recipe {
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@Override
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public String getDisplayName() {
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return "Remove underscores from private class field names";
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}
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@Override
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public String getDescription() {
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return "Removes prefix or suffix underscores from private class field names and adds `this.` to all field accesses for clarity and consistency.";
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}
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@Override
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public TreeVisitor<?, ExecutionContext> getVisitor() {
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return new JavaVisitor<ExecutionContext>() {
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@Override
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public J visitVariableDeclarations(J.VariableDeclarations multiVariable, ExecutionContext ctx) {
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J.VariableDeclarations mv = (J.VariableDeclarations) super.visitVariableDeclarations(multiVariable, ctx);
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if (!mv.hasModifier(J.Modifier.Type.Private)) {
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return mv;
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}
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Cursor parent = getCursor().getParentTreeCursor();
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if (!(parent.getValue() instanceof J.Block && parent.getParentTreeCursor().getValue() instanceof J.ClassDeclaration)) {
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return mv;
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}
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for (J.VariableDeclarations.NamedVariable variable : mv.getVariables()) {
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String oldName = variable.getSimpleName();
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if (oldName.startsWith("_") || oldName.endsWith("_")) {
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String newName = oldName.startsWith("_") ? oldName.substring(1) : oldName.substring(0, oldName.length() - 1);
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doAfterVisit(new AddThisToFieldUses(variable));
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doAfterVisit(new RenameVariable(variable, newName));
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}
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}
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return mv;
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}
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};
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}
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private static class AddThisToFieldUses extends JavaVisitor<ExecutionContext> {
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private final JavaType.Variable fieldType;
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public AddThisToFieldUses(J.VariableDeclarations.NamedVariable field) {
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this.fieldType = field.getVariableType();
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}
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@Override
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public J visitIdentifier(J.Identifier identifier, ExecutionContext ctx) {
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J.Identifier id = (J.Identifier) super.visitIdentifier(identifier, ctx);
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if (id.getFieldType() != null && id.getFieldType().equals(this.fieldType)) {
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if (getCursor().getParentTreeCursor().getValue() instanceof J.VariableDeclarations.NamedVariable) {
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return id;
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}
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if (getCursor().getParentTreeCursor().getValue() instanceof J.FieldAccess) {
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return id;
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}
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return new J.FieldAccess(
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Tree.randomId(),
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identifier.getPrefix(),
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Markers.EMPTY,
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new J.Identifier(
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Tree.randomId(),
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Space.EMPTY,
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Markers.EMPTY,
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emptyList(),
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"this",
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identifier.getType(),
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null
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),
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JLeftPadded.build(identifier.withPrefix(Space.EMPTY).withSimpleName(id.getSimpleName())),
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identifier.getType()
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);
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}
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return id;
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}
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}
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}

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

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/*
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* Copyright 2025 the original author or authors.
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* <p>
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* Licensed under the Moderne Source Available License (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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* <p>
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* https://docs.moderne.io/licensing/moderne-source-available-license
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* <p>
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.openrewrite.staticanalysis;
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import org.junit.jupiter.api.Test;
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import org.openrewrite.DocumentExample;
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import org.openrewrite.test.RecipeSpec;
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import org.openrewrite.test.RewriteTest;
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import static org.openrewrite.java.Assertions.java;
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class RemovePrivateFieldUnderscoresTest implements RewriteTest {
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@Override
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public void defaults(RecipeSpec spec) {
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spec.recipe(new RemovePrivateFieldUnderscores());
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}
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@DocumentExample
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@Test
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void removesPrefixUnderscore() {
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rewriteRun(
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//language=java
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java(
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"""
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public class ParseLocation {
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private String _ruleName;
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public String getRuleName() {
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return _ruleName;
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}
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public void setRuleName(String ruleName) {
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_ruleName = ruleName;
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}
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}
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""",
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"""
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public class ParseLocation {
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private String ruleName;
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public String getRuleName() {
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return this.ruleName;
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}
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public void setRuleName(String ruleName) {
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this.ruleName = ruleName;
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}
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}
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"""
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)
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);
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}
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@Test
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void removesSuffixUnderscore() {
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rewriteRun(
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//language=java
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java(
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"""
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public class ParseLocation {
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private String ruleName_;
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public String getRuleName() {
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return ruleName_;
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}
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public void setRuleName(String ruleName) {
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ruleName_ = ruleName;
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}
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}
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""",
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"""
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public class ParseLocation {
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private String ruleName;
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public String getRuleName() {
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return this.ruleName;
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}
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public void setRuleName(String ruleName) {
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this.ruleName = ruleName;
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}
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}
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"""
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)
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);
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}
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@Test
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void handlesFieldAccessInOtherMethods() {
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rewriteRun(
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//language=java
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java(
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"""
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public class Calculator {
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private int _operand1;
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private int operand2_;
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public Calculator(int a, int b) {
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_operand1 = a;
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operand2_ = b;
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}
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public int sum() {
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return _operand1 + operand2_;
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}
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}
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""",
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"""
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public class Calculator {
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private int operand1;
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private int operand2;
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public Calculator(int a, int b) {
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this.operand1 = a;
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this.operand2 = b;
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}
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public int sum() {
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return this.operand1 + this.operand2;
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}
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}
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"""
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)
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);
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}
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@Test
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void handlesFieldsAlreadyQualifiedWithThis() {
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rewriteRun(
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//language=java
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java(
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"""
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public class ParseLocation {
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private String _ruleName;
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public String getRuleName() {
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return this._ruleName;
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}
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public void setRuleName(String ruleName) {
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this._ruleName = ruleName;
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}
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}
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""",
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"""
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public class ParseLocation {
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private String ruleName;
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public String getRuleName() {
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return this.ruleName;
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}
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public void setRuleName(String ruleName) {
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this.ruleName = ruleName;
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}
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}
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"""
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)
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);
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}
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@Test
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void doesNotChangeNonPrivateFields() {
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rewriteRun(
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//language=java
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java(
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"""
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public class MyClass {
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public String _publicField;
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protected String _protectedField;
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String packagePrivateField_;
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}
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"""
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)
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);
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}
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@Test
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void doesNotChangeLocalVariables() {
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rewriteRun(
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//language=java
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java(
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"""
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public class MyClass {
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public void myMethod() {
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String _localVar = "prefixUnderscore";
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String localVar_ = "suffixUnderscore";
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}
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}
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"""
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)
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);
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}
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}

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