org.sonar.java.checks.ForLoopFalseConditionCheck.java Source code

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Here is the source code for org.sonar.java.checks.ForLoopFalseConditionCheck.java

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/*
 * SonarQube Java
 * Copyright (C) 2012-2017 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.apache.commons.lang.BooleanUtils;
import org.sonar.check.Rule;
import org.sonar.java.model.LiteralUtils;
import org.sonar.plugins.java.api.tree.BinaryExpressionTree;
import org.sonar.plugins.java.api.tree.ExpressionTree;
import org.sonar.plugins.java.api.tree.ForStatementTree;
import org.sonar.plugins.java.api.tree.LiteralTree;
import org.sonar.plugins.java.api.tree.Tree;
import org.sonar.plugins.java.api.tree.UnaryExpressionTree;

import javax.annotation.CheckForNull;

@Rule(key = "S2252")
public class ForLoopFalseConditionCheck extends AbstractForLoopRule {

    @Override
    public void visitForStatement(ForStatementTree forStatement) {
        ExpressionTree condition = forStatement.condition();
        if (condition != null
                && (isAlwaysFalseCondition(condition) || isConditionFalseAtInitialization(forStatement))) {
            reportIssue(condition, "This loop will never execute.");
        }
    }

    private static boolean isAlwaysFalseCondition(ExpressionTree expression) {
        if (expression.is(Tree.Kind.BOOLEAN_LITERAL)) {
            return BooleanUtils.isFalse(booleanLiteralValue(expression));
        }
        if (expression.is(Tree.Kind.LOGICAL_COMPLEMENT)) {
            ExpressionTree subExpression = ((UnaryExpressionTree) expression).expression();
            return BooleanUtils.isTrue(booleanLiteralValue(subExpression));
        }
        return false;
    }

    @CheckForNull
    private static Boolean booleanLiteralValue(ExpressionTree expression) {
        if (expression.is(Tree.Kind.BOOLEAN_LITERAL)) {
            return Boolean.valueOf(((LiteralTree) expression).value());
        }
        return null;
    }

    private static boolean isConditionFalseAtInitialization(ForStatementTree forStatement) {
        Iterable<ForLoopInitializer> initializers = ForLoopInitializer.list(forStatement);
        ExpressionTree condition = forStatement.condition();
        if (!condition.is(Tree.Kind.GREATER_THAN, Tree.Kind.GREATER_THAN_OR_EQUAL_TO, Tree.Kind.LESS_THAN,
                Tree.Kind.LESS_THAN_OR_EQUAL_TO)) {
            return false;
        }
        BinaryExpressionTree binaryCondition = (BinaryExpressionTree) condition;
        Integer leftOperand = eval(binaryCondition.leftOperand(), initializers);
        Integer rightOperand = eval(binaryCondition.rightOperand(), initializers);
        if (leftOperand != null && rightOperand != null) {
            return !evaluateCondition(condition, leftOperand, rightOperand);
        }
        return false;
    }

    private static boolean evaluateCondition(ExpressionTree condition, int leftOperand, int rightOperand) {
        boolean conditionValue;
        switch (condition.kind()) {
        case GREATER_THAN:
            conditionValue = leftOperand > rightOperand;
            break;
        case GREATER_THAN_OR_EQUAL_TO:
            conditionValue = leftOperand >= rightOperand;
            break;
        case LESS_THAN:
            conditionValue = leftOperand < rightOperand;
            break;
        case LESS_THAN_OR_EQUAL_TO:
            conditionValue = leftOperand <= rightOperand;
            break;
        default:
            conditionValue = true;
        }
        return conditionValue;
    }

    private static Integer eval(ExpressionTree expression, Iterable<ForLoopInitializer> initializers) {
        Integer intLiteralValue = LiteralUtils.intLiteralValue(expression);
        if (intLiteralValue == null) {
            for (ForLoopInitializer initializer : initializers) {
                if (initializer.hasSameIdentifier(expression)) {
                    intLiteralValue = initializer.value();
                }
            }
        }
        return intLiteralValue;
    }

}