plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/performance/ObjectAllocationInLoopInspection.java

/*
 * Copyright 2003-2007 Dave Griffith, Bas Leijdekkers
 *
 * 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 com.siyeh.ig.performance;

import com.intellij.psi.*;
import com.intellij.psi.util.PsiTreeUtil;
import com.siyeh.InspectionGadgetsBundle;
import com.siyeh.ig.BaseInspection;
import com.siyeh.ig.BaseInspectionVisitor;
import com.siyeh.ig.psiutils.ControlFlowUtils;
import org.jetbrains.annotations.NotNull;

public class ObjectAllocationInLoopInspection extends BaseInspection {

  @Override
  @NotNull
  public String getDisplayName() {
    return InspectionGadgetsBundle.message(
      "object.allocation.in.loop.display.name");
  }

  @Override
  @NotNull
  protected String buildErrorString(Object... infos) {
    return InspectionGadgetsBundle.message(
      "object.allocation.in.loop.problem.descriptor");
  }

  @Override
  public BaseInspectionVisitor buildVisitor() {
    return new ObjectAllocationInLoopsVisitor();
  }

  private static class ObjectAllocationInLoopsVisitor
    extends BaseInspectionVisitor {

    @Override
    public void visitNewExpression(@NotNull PsiNewExpression expression) {
      super.visitNewExpression(expression);
      if (!ControlFlowUtils.isInLoop(expression)) {
        return;
      }
      if (ControlFlowUtils.isInExitStatement(expression)) {
        return;
      }
      final PsiStatement newExpressionStatement =
        PsiTreeUtil.getParentOfType(expression, PsiStatement.class);
      if (newExpressionStatement == null) {
        return;
      }
      final PsiStatement parentStatement =
        PsiTreeUtil.getParentOfType(newExpressionStatement,
                                    PsiStatement.class);
      if (!ControlFlowUtils.statementMayCompleteNormally(
        parentStatement)) {
        return;
      }
      if (isAllocatedOnlyOnce(expression)) {
        return;
      }
      registerNewExpressionError(expression);
    }

    private static boolean isAllocatedOnlyOnce(
      PsiNewExpression expression) {
      final PsiElement parent = expression.getParent();
      if (!(parent instanceof PsiAssignmentExpression)) {
        return false;
      }
      final PsiAssignmentExpression assignmentExpression =
        (PsiAssignmentExpression)parent;
      final PsiExpression lExpression =
        assignmentExpression.getLExpression();
      if (!(lExpression instanceof PsiReferenceExpression)) {
        return false;
      }
      final PsiIfStatement ifStatement =
        PsiTreeUtil.getParentOfType(assignmentExpression,
                                    PsiIfStatement.class);
      if (ifStatement == null) {
        return false;
      }
      final PsiExpression condition = ifStatement.getCondition();
      if (!(condition instanceof PsiBinaryExpression)) {
        return false;
      }
      final PsiBinaryExpression binaryExpression =
        (PsiBinaryExpression)condition;
      if (binaryExpression.getOperationTokenType() !=
          JavaTokenType.EQEQ) {
        return false;
      }
      final PsiReferenceExpression referenceExpression =
        (PsiReferenceExpression)lExpression;
      final PsiExpression lhs = binaryExpression.getLOperand();
      final PsiExpression rhs = binaryExpression.getROperand();
      if (lhs instanceof PsiLiteralExpression) {
        if (!"null".equals(lhs.getText())) {
          return false;
        }
        if (!(rhs instanceof PsiReferenceExpression)) {
          return false;
        }
        return referenceExpression.getText().equals(rhs.getText());
      }
      else if (rhs instanceof PsiLiteralExpression) {
        if (!"null".equals(rhs.getText())) {
          return false;
        }
        if (!(lhs instanceof PsiReferenceExpression)) {
          return false;
        }
        return referenceExpression.getText().equals(lhs.getText());
      }
      else {
        return false;
      }
    }
  }
}