String.length() == 0should be replaced with + *
String.isEmpty(). + */ +@Rule(key = "S7158") +public class StringIsEmptyCheck extends IssuableSubscriptionVisitor implements JavaVersionAwareVisitor { + + private static final MethodMatchers LENGTH_METHOD = MethodMatchers.create() + .ofTypes("java.lang.String") + .names("length") + .addWithoutParametersMatcher() + .build(); + + private static final Kind[] TARGETED_BINARY_OPERATOR_TREES = { + Kind.EQUAL_TO, + Kind.NOT_EQUAL_TO, + Kind.LESS_THAN, + Kind.LESS_THAN_OR_EQUAL_TO, + Kind.GREATER_THAN, + Kind.GREATER_THAN_OR_EQUAL_TO + }; + + // `String.isEmpty()` is available since Java 6. + @Override + public boolean isCompatibleWithJavaVersion(JavaVersion version) { + return version.isJava6Compatible(); + } + + @Override + public List
length() OP VALUE. + */ + private static boolean isComparisonOnRight(BinaryExpressionTree tree, boolean rightIsZero, boolean rightIsOne) { + return (tree.is(Kind.EQUAL_TO, Kind.LESS_THAN_OR_EQUAL_TO, Kind.NOT_EQUAL_TO, Kind.GREATER_THAN) && rightIsZero) + || (tree.is(Kind.LESS_THAN, Kind.GREATER_THAN_OR_EQUAL_TO) && rightIsOne); + } + + /** + * Check the comparison for
VALUE OP length(). + */ + private static boolean isComparisonOnLeft(boolean leftIsZero, boolean leftIsOne, BinaryExpressionTree tree) { + return (leftIsZero && tree.is(Kind.EQUAL_TO, Kind.GREATER_THAN_OR_EQUAL_TO, Kind.NOT_EQUAL_TO, Kind.LESS_THAN)) + || (leftIsOne && tree.is(Kind.GREATER_THAN, Kind.LESS_THAN_OR_EQUAL_TO)); + } +} diff --git a/java-checks/src/test/java/org/sonar/java/checks/StringIsEmptyCheckTest.java b/java-checks/src/test/java/org/sonar/java/checks/StringIsEmptyCheckTest.java new file mode 100644 index 00000000000..5249027d283 --- /dev/null +++ b/java-checks/src/test/java/org/sonar/java/checks/StringIsEmptyCheckTest.java @@ -0,0 +1,45 @@ +/* + * SonarQube Java + * Copyright (C) 2012-2024 SonarSource SA + * mailto:info AT sonarsource DOT com + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 3 of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with this program; if not, write to the Free Software Foundation, + * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + */ +package org.sonar.java.checks; + +import org.junit.jupiter.api.Test; +import org.sonar.java.checks.verifier.CheckVerifier; + +import static org.sonar.java.checks.verifier.TestUtils.mainCodeSourcesPath; + +class StringIsEmptyCheckTest { + + @Test + void test() { + CheckVerifier.newVerifier() + .onFile(mainCodeSourcesPath("checks/StringIsEmptyCheckSample.java")) + .withCheck(new StringIsEmptyCheck()) + .verifyIssues(); + } + + @Test + void testOlderJavaVersion() { + CheckVerifier.newVerifier() + .onFile(mainCodeSourcesPath("checks/StringIsEmptyCheckSample.java")) + .withCheck(new StringIsEmptyCheck()) + .withJavaVersion(5) + .verifyNoIssues(); + } +} diff --git a/sonar-java-plugin/src/main/resources/org/sonar/l10n/java/rules/java/S7158.html b/sonar-java-plugin/src/main/resources/org/sonar/l10n/java/rules/java/S7158.html new file mode 100644 index 00000000000..5553eea55d7 --- /dev/null +++ b/sonar-java-plugin/src/main/resources/org/sonar/l10n/java/rules/java/S7158.html @@ -0,0 +1,24 @@ +
Calling String.isEmpty() clearly communicates the code’s intention, which is to test if the string is empty. Using
+String.length() == 0 is less direct and makes the code less readable.
+if ("string".length() == 0) { /* … */ } // Noncompliant
+
+if ("string".length() > 0) { /* … */ } // Noncompliant
+
+
+if ("string".isEmpty()){ /* … */ }
+
+if (!"string".isEmpty()){ /* … */ }
+
+