lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/JavaPerformanceDetector.java - platform/tools/base - Git at Google

 /*
  * Copyright (C) 2012 The Android Open Source Project
  *
  * 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.android.tools.lint.checks;

 import static com.android.SdkConstants.SUPPORT_LIB_ARTIFACT;
 import static com.android.tools.lint.client.api.JavaParser.TYPE_BOOLEAN;
 import static com.android.tools.lint.client.api.JavaParser.TYPE_BOOLEAN_WRAPPER;
 import static com.android.tools.lint.client.api.JavaParser.TYPE_BYTE_WRAPPER;
 import static com.android.tools.lint.client.api.JavaParser.TYPE_CHARACTER_WRAPPER;
 import static com.android.tools.lint.client.api.JavaParser.TYPE_DOUBLE_WRAPPER;
 import static com.android.tools.lint.client.api.JavaParser.TYPE_FLOAT_WRAPPER;
 import static com.android.tools.lint.client.api.JavaParser.TYPE_INT;
 import static com.android.tools.lint.client.api.JavaParser.TYPE_INTEGER_WRAPPER;
 import static com.android.tools.lint.client.api.JavaParser.TYPE_LONG_WRAPPER;
 import static com.android.tools.lint.detector.api.LintUtils.skipParentheses;

 import com.android.annotations.NonNull;
 import com.android.annotations.Nullable;
 import com.android.tools.lint.client.api.JavaEvaluator;
 import com.android.tools.lint.detector.api.Category;
 import com.android.tools.lint.detector.api.Detector;
 import com.android.tools.lint.detector.api.Implementation;
 import com.android.tools.lint.detector.api.Issue;
 import com.android.tools.lint.detector.api.JavaContext;
 import com.android.tools.lint.detector.api.Scope;
 import com.android.tools.lint.detector.api.Severity;
 import com.android.tools.lint.detector.api.TextFormat;
 import com.google.common.collect.Sets;
 import com.google.common.collect.Sets.SetView;
 import com.intellij.psi.JavaElementVisitor;
 import com.intellij.psi.JavaRecursiveElementVisitor;
 import com.intellij.psi.PsiAssignmentExpression;
 import com.intellij.psi.PsiBinaryExpression;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiExpression;
 import com.intellij.psi.PsiIdentifier;
 import com.intellij.psi.PsiIfStatement;
 import com.intellij.psi.PsiJavaCodeReferenceElement;
 import com.intellij.psi.PsiMethod;
 import com.intellij.psi.PsiMethodCallExpression;
 import com.intellij.psi.PsiNewExpression;
 import com.intellij.psi.PsiParenthesizedExpression;
 import com.intellij.psi.PsiPrefixExpression;
 import com.intellij.psi.PsiReferenceExpression;
 import com.intellij.psi.PsiSuperExpression;
 import com.intellij.psi.PsiThisExpression;
 import com.intellij.psi.PsiThrowStatement;
 import com.intellij.psi.PsiType;
 import com.intellij.psi.util.PsiTreeUtil;

 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;

 /**
  * Looks for performance issues in Java files, such as memory allocations during
  * drawing operations and using HashMap instead of SparseArray.
  */
 public class JavaPerformanceDetector extends Detector implements Detector.JavaPsiScanner {

     private static final Implementation IMPLEMENTATION = new Implementation(
             JavaPerformanceDetector.class,
             Scope.JAVA_FILE_SCOPE);

     /** Allocating objects during a paint method */
     public static final Issue PAINT_ALLOC = Issue.create(
             "DrawAllocation", //$NON-NLS-1$
             "Memory allocations within drawing code",

             "You should avoid allocating objects during a drawing or layout operation. These " +
             "are called frequently, so a smooth UI can be interrupted by garbage collection " +
             "pauses caused by the object allocations.\n" +
             "\n" +
             "The way this is generally handled is to allocate the needed objects up front " +
             "and to reuse them for each drawing operation.\n" +
             "\n" +
             "Some methods allocate memory on your behalf (such as `Bitmap.create`), and these " +
             "should be handled in the same way.",

             Category.PERFORMANCE,
             9,
             Severity.WARNING,
             IMPLEMENTATION);

     /** Using HashMaps where SparseArray would be better */
     public static final Issue USE_SPARSE_ARRAY = Issue.create(
             "UseSparseArrays", //$NON-NLS-1$
             "HashMap can be replaced with SparseArray",

             "For maps where the keys are of type integer, it's typically more efficient to " +
             "use the Android `SparseArray` API. This check identifies scenarios where you might " +
             "want to consider using `SparseArray` instead of `HashMap` for better performance.\n" +
             "\n" +
             "This is *particularly* useful when the value types are primitives like ints, " +
             "where you can use `SparseIntArray` and avoid auto-boxing the values from `int` to " +
             "`Integer`.\n" +
             "\n" +
             "If you need to construct a `HashMap` because you need to call an API outside of " +
             "your control which requires a `Map`, you can suppress this warning using for " +
             "example the `@SuppressLint` annotation.",

             Category.PERFORMANCE,
             4,
             Severity.WARNING,
             IMPLEMENTATION);

     /** Using {@code new Integer()} instead of the more efficient {@code Integer.valueOf} */
     public static final Issue USE_VALUE_OF = Issue.create(
             "UseValueOf", //$NON-NLS-1$
             "Should use `valueOf` instead of `new`",

             "You should not call the constructor for wrapper classes directly, such as" +
             "`new Integer(42)`. Instead, call the `valueOf` factory method, such as " +
             "`Integer.valueOf(42)`. This will typically use less memory because common integers " +
             "such as 0 and 1 will share a single instance.",

             Category.PERFORMANCE,
             4,
             Severity.WARNING,
             IMPLEMENTATION);

     static final String ON_MEASURE = "onMeasure";
     static final String ON_DRAW = "onDraw";
     static final String ON_LAYOUT = "onLayout";
     private static final String LAYOUT = "layout";
     private static final String HASH_MAP = "java.util.HashMap";
     private static final String SPARSE_ARRAY = "android.util.SparseArray";
     public static final String CLASS_CANVAS = "android.graphics.Canvas";

     /** Constructs a new {@link JavaPerformanceDetector} check */
     public JavaPerformanceDetector() {
     }

     // ---- Implements JavaScanner ----

     @Override
     public List<Class<? extends PsiElement>> getApplicablePsiTypes() {
         List<Class<? extends PsiElement>> types = new ArrayList<Class<? extends PsiElement>>(3);
         types.add(PsiNewExpression.class);
         types.add(PsiMethod.class);
         types.add(PsiMethodCallExpression.class);
         return types;
     }

     @Override
     public JavaElementVisitor createPsiVisitor(@NonNull JavaContext context) {
         return new PerformanceVisitor(context);
     }

     private static class PerformanceVisitor extends JavaElementVisitor {
         private final JavaContext mContext;
         private final boolean mCheckMaps;
         private final boolean mCheckAllocations;
         private final boolean mCheckValueOf;
         /** Whether allocations should be "flagged" in the current method */
         private boolean mFlagAllocations;

         public PerformanceVisitor(JavaContext context) {
             mContext = context;

             mCheckAllocations = context.isEnabled(PAINT_ALLOC);
             mCheckMaps = context.isEnabled(USE_SPARSE_ARRAY);
             mCheckValueOf = context.isEnabled(USE_VALUE_OF);
         }

         @Override
         public void visitMethod(PsiMethod node) {
             mFlagAllocations = isBlockedAllocationMethod(node);
         }

         @Override
         public void visitNewExpression(PsiNewExpression node) {
             String typeName = null;
             PsiJavaCodeReferenceElement classReference = node.getClassReference();
             if (mCheckMaps || mCheckValueOf) {
                 if (classReference != null) {
                     typeName = classReference.getQualifiedName();
                 }
             }

             if (mCheckMaps) {
                 // TODO: Should we handle factory method constructions of HashMaps as well,
                 // e.g. via Guava? This is a bit trickier since we need to infer the type
                 // arguments from the calling context.
                 if (HASH_MAP.equals(typeName)) {
                     checkHashMap(node, classReference);
                 } else if (SPARSE_ARRAY.equals(typeName)) {
                     checkSparseArray(node, classReference);
                 }
             }

             if (mCheckValueOf) {
                 if (typeName != null
                         && (typeName.equals(TYPE_INTEGER_WRAPPER)
                         || typeName.equals(TYPE_BOOLEAN_WRAPPER)
                         || typeName.equals(TYPE_FLOAT_WRAPPER)
                         || typeName.equals(TYPE_CHARACTER_WRAPPER)
                         || typeName.equals(TYPE_LONG_WRAPPER)
                         || typeName.equals(TYPE_DOUBLE_WRAPPER)
                         || typeName.equals(TYPE_BYTE_WRAPPER))
                         //&& node.astTypeReference().astParts().size() == 1
                         && node.getArgumentList() != null
                         && node.getArgumentList().getExpressions().length == 1) {
                     String argument = node.getArgumentList().getExpressions()[0].getText();
                     mContext.report(USE_VALUE_OF, node, mContext.getLocation(node), getUseValueOfErrorMessage(
                             typeName, argument));
                 }
             }

             if (mFlagAllocations
                     && !(skipParentheses(node.getParent()) instanceof PsiThrowStatement)
                     && mCheckAllocations) {
                 // Make sure we're still inside the method declaration that marked
                 // mInDraw as true, in case we've left it and we're in a static
                 // block or something:
                 PsiMethod method = PsiTreeUtil.getParentOfType(node, PsiMethod.class);
                 if (method != null && isBlockedAllocationMethod(method)
                         && !isLazilyInitialized(node)) {
                     reportAllocation(node);
                 }
             }
         }

         private void reportAllocation(PsiElement node) {
             mContext.report(PAINT_ALLOC, node, mContext.getLocation(node),
                 "Avoid object allocations during draw/layout operations (preallocate and " +
                 "reuse instead)");
         }

         @Override
         public void visitMethodCallExpression(PsiMethodCallExpression node) {
             if (!mFlagAllocations) {
                 return;
             }
             PsiReferenceExpression expression = node.getMethodExpression();
             PsiElement qualifier = expression.getQualifier();
             if (qualifier == null) {
                 return;
             }
             String methodName = expression.getReferenceName();
             if (methodName == null) {
                 return;
             }
             // Look for forbidden methods
             if (methodName.equals("createBitmap")                              //$NON-NLS-1$
                     || methodName.equals("createScaledBitmap")) {              //$NON-NLS-1$
                 PsiMethod method = node.resolveMethod();
                 if (method != null && mContext.getEvaluator().isMemberInClass(method,
                         "android.graphics.Bitmap") && !isLazilyInitialized(node)) {
                     reportAllocation(node);
                 }
             } else if (methodName.startsWith("decode")) {                      //$NON-NLS-1$
                 // decodeFile, decodeByteArray, ...
                 PsiMethod method = node.resolveMethod();
                 if (method != null && mContext.getEvaluator().isMemberInClass(method,
                         "android.graphics.BitmapFactory") && !isLazilyInitialized(node)) {
                     reportAllocation(node);
                 }
             } else if (methodName.equals("getClipBounds")) {                   //$NON-NLS-1$
                 if (node.getArgumentList().getExpressions().length == 0) {
                     mContext.report(PAINT_ALLOC, node, mContext.getLocation(node),
                             "Avoid object allocations during draw operations: Use " +
                             "`Canvas.getClipBounds(Rect)` instead of `Canvas.getClipBounds()` " +
                             "which allocates a temporary `Rect`");
                 }
             }
         }

         /**
          * Check whether the given invocation is done as a lazy initialization,
          * e.g. {@code if (foo == null) foo = new Foo();}.
          * <p>
          * This tries to also handle the scenario where the check is on some
          * <b>other</b> variable - e.g.
          * <pre>
          *    if (foo == null) {
          *        foo == init1();
          *        bar = new Bar();
          *    }
          * </pre>
          * or
          * <pre>
          *    if (!initialized) {
          *        initialized = true;
          *        bar = new Bar();
          *    }
          * </pre>
          */
         private static boolean isLazilyInitialized(PsiElement node) {
             PsiElement curr = node.getParent();
             while (curr != null) {
                 if (curr instanceof PsiMethod) {
                     return false;
                 } else if (curr instanceof PsiIfStatement) {
                     PsiIfStatement ifNode = (PsiIfStatement) curr;
                     // See if the if block represents a lazy initialization:
                     // compute all variable names seen in the condition
                     // (e.g. for "if (foo == null || bar != foo)" the result is "foo,bar"),
                     // and then compute all variables assigned to in the if body,
                     // and if there is an overlap, we'll consider the whole if block
                     // guarded (so lazily initialized and an allocation we won't complain
                     // about.)
                     List<String> assignments = new ArrayList<String>();
                     AssignmentTracker visitor = new AssignmentTracker(assignments);
                     if (ifNode.getThenBranch() != null) {
                         ifNode.getThenBranch().accept(visitor);
                     }
                     if (!assignments.isEmpty()) {
                         List<String> references = new ArrayList<String>();
                         addReferencedVariables(references, ifNode.getCondition());
                         if (!references.isEmpty()) {
                             SetView<String> intersection = Sets.intersection(
                                     new HashSet<String>(assignments),
                                     new HashSet<String>(references));
                             return !intersection.isEmpty();
                         }
                     }
                     return false;

                 }
                 curr = curr.getParent();
             }

             return false;
         }

         /** Adds any variables referenced in the given expression into the given list */
         private static void addReferencedVariables(
                 @NonNull Collection<String> variables,
                 @Nullable PsiExpression expression) {
             if (expression instanceof PsiBinaryExpression) {
                 PsiBinaryExpression binary = (PsiBinaryExpression) expression;
                 addReferencedVariables(variables, binary.getLOperand());
                 addReferencedVariables(variables, binary.getROperand());
             } else if (expression instanceof PsiPrefixExpression) {
                 PsiPrefixExpression unary = (PsiPrefixExpression) expression;
                 addReferencedVariables(variables, unary.getOperand());
             } else if (expression instanceof PsiParenthesizedExpression) {
                 PsiParenthesizedExpression exp = (PsiParenthesizedExpression) expression;
                 addReferencedVariables(variables, exp.getExpression());
             } else if (expression instanceof PsiIdentifier) {
                 PsiIdentifier reference = (PsiIdentifier) expression;
                 variables.add(reference.getText());
             } else if (expression instanceof PsiReferenceExpression) {
                 PsiReferenceExpression ref = (PsiReferenceExpression) expression;
                 PsiElement qualifier = ref.getQualifier();
                 if (qualifier != null) {
                     if (qualifier instanceof PsiThisExpression ||
                             qualifier instanceof PsiSuperExpression) {
                         variables.add(ref.getReferenceName());
                     }
                 } else {
                     variables.add(ref.getReferenceName());
                 }
             }
         }

         /**
          * Returns whether the given method declaration represents a method
          * where allocating objects is not allowed for performance reasons
          */
         private boolean isBlockedAllocationMethod(
                 @NonNull PsiMethod node) {
             JavaEvaluator evaluator = mContext.getEvaluator();
             return isOnDrawMethod(evaluator, node)
                     || isOnMeasureMethod(evaluator, node)
                     || isOnLayoutMethod(evaluator, node)
                     || isLayoutMethod(evaluator, node);
         }

         /**
          * Returns true if this method looks like it's overriding android.view.View's
          * {@code protected void onDraw(Canvas canvas)}
          */
         private static boolean isOnDrawMethod(
                 @NonNull JavaEvaluator evaluator,
                 @NonNull PsiMethod node) {
             return ON_DRAW.equals(node.getName()) && evaluator.parametersMatch(node, CLASS_CANVAS);
         }

         /**
          * Returns true if this method looks like it's overriding
          * android.view.View's
          * {@code protected void onLayout(boolean changed, int left, int top,
          *      int right, int bottom)}
          */
         private static boolean isOnLayoutMethod(
                 @NonNull JavaEvaluator evaluator,
                 @NonNull PsiMethod node) {
             return ON_LAYOUT.equals(node.getName()) && evaluator.parametersMatch(node,
                     TYPE_BOOLEAN, TYPE_INT, TYPE_INT, TYPE_INT, TYPE_INT);
         }

         /**
          * Returns true if this method looks like it's overriding android.view.View's
          * {@code protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)}
          */
         private static boolean isOnMeasureMethod(
                 @NonNull JavaEvaluator evaluator,
                 @NonNull PsiMethod node) {
             return ON_MEASURE.equals(node.getName()) && evaluator.parametersMatch(node,
                     TYPE_INT, TYPE_INT);
         }

         /**
          * Returns true if this method looks like it's overriding android.view.View's
          * {@code public void layout(int l, int t, int r, int b)}
          */
         private static boolean isLayoutMethod(
                 @NonNull JavaEvaluator evaluator,
                 @NonNull PsiMethod node) {
             return LAYOUT.equals(node.getName()) && evaluator.parametersMatch(node,
                     TYPE_INT, TYPE_INT, TYPE_INT, TYPE_INT);
         }

         /**
          * Checks whether the given constructor call and type reference refers
          * to a HashMap constructor call that is eligible for replacement by a
          * SparseArray call instead
          */
         private void checkHashMap(
                 @NonNull PsiNewExpression node,
                 @NonNull PsiJavaCodeReferenceElement reference) {
             PsiType[] types = reference.getTypeParameters();
             if (types.length == 2) {
                 PsiType first = types[0];
                 String typeName = first.getCanonicalText();
                 int minSdk = mContext.getMainProject().getMinSdk();
                 if (TYPE_INTEGER_WRAPPER.equals(typeName) || TYPE_BYTE_WRAPPER.equals(typeName)) {
                     String valueType = types[1].getCanonicalText();
                     if (valueType.equals(TYPE_INTEGER_WRAPPER)) {
                         mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
                             "Use new `SparseIntArray(...)` instead for better performance");
                     } else if (valueType.equals(TYPE_LONG_WRAPPER) && minSdk >= 18) {
                         mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
                                 "Use `new SparseLongArray(...)` instead for better performance");
                     } else if (valueType.equals(TYPE_BOOLEAN_WRAPPER)) {
                         mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
                                 "Use `new SparseBooleanArray(...)` instead for better performance");
                     } else {
                         mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
                             String.format(
                                 "Use `new SparseArray<%1$s>(...)` instead for better performance",
                               valueType.substring(valueType.lastIndexOf('.') + 1)));
                     }
                 } else if (TYPE_LONG_WRAPPER.equals(typeName) && (minSdk >= 16 ||
                         Boolean.TRUE == mContext.getMainProject().dependsOn(
                                 SUPPORT_LIB_ARTIFACT))) {
                     boolean useBuiltin = minSdk >= 16;
                     String message = useBuiltin ?
                             "Use `new LongSparseArray(...)` instead for better performance" :
                             "Use `new android.support.v4.util.LongSparseArray(...)` instead for better performance";
                     mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
                             message);
                 }
             }
         }

         private void checkSparseArray(
                 @NonNull PsiNewExpression node,
                 @NonNull PsiJavaCodeReferenceElement reference) {
             PsiType[] types = reference.getTypeParameters();
             if (types.length == 1) {
                 String valueType = types[0].getCanonicalText();
                 if (valueType.equals(TYPE_INTEGER_WRAPPER)) {
                     mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
                         "Use `new SparseIntArray(...)` instead for better performance");
                 } else if (valueType.equals(TYPE_BOOLEAN_WRAPPER)) {
                     mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
                             "Use `new SparseBooleanArray(...)` instead for better performance");
                 }
             }
         }
     }

     private static String getUseValueOfErrorMessage(String typeName, String argument) {
         // Keep in sync with {@link #getReplacedType} below
         return String.format("Use `%1$s.valueOf(%2$s)` instead",
                 typeName.substring(typeName.lastIndexOf('.') + 1), argument);
     }

     /**
      * For an error message for an {@link #USE_VALUE_OF} issue reported by this detector,
      * returns the type being replaced. Intended to use for IDE quickfix implementations.
      */
     @SuppressWarnings("unused") // Used by the IDE
     @Nullable
     public static String getReplacedType(@NonNull String message, @NonNull TextFormat format) {
         message = format.toText(message);
         int index = message.indexOf('.');
         if (index != -1 && message.startsWith("Use ")) {
             return message.substring(4, index);
         }
         return null;
     }

     /** Visitor which records variable names assigned into */
     private static class AssignmentTracker extends JavaRecursiveElementVisitor {
         private final Collection<String> mVariables;

         public AssignmentTracker(Collection<String> variables) {
             mVariables = variables;
         }

         @Override
         public void visitAssignmentExpression(PsiAssignmentExpression node) {
             super.visitAssignmentExpression(node);

             PsiExpression left = node.getLExpression();
             if (left instanceof PsiReferenceExpression) {
                 PsiReferenceExpression ref = (PsiReferenceExpression) left;
                 if (ref.getQualifier() instanceof PsiThisExpression ||
                         ref.getQualifier() instanceof PsiSuperExpression) {
                     mVariables.add(ref.getReferenceName());
                 } else {
                     mVariables.add(ref.getText());
                 }
             } else if (left instanceof PsiIdentifier) {
                 mVariables.add(left.getText());
             }
         }
     }
 }
	/*
	* Copyright (C) 2012 The Android Open Source Project
	*
	* 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.android.tools.lint.checks;

	import static com.android.SdkConstants.SUPPORT_LIB_ARTIFACT;
	import static com.android.tools.lint.client.api.JavaParser.TYPE_BOOLEAN;
	import static com.android.tools.lint.client.api.JavaParser.TYPE_BOOLEAN_WRAPPER;
	import static com.android.tools.lint.client.api.JavaParser.TYPE_BYTE_WRAPPER;
	import static com.android.tools.lint.client.api.JavaParser.TYPE_CHARACTER_WRAPPER;
	import static com.android.tools.lint.client.api.JavaParser.TYPE_DOUBLE_WRAPPER;
	import static com.android.tools.lint.client.api.JavaParser.TYPE_FLOAT_WRAPPER;
	import static com.android.tools.lint.client.api.JavaParser.TYPE_INT;
	import static com.android.tools.lint.client.api.JavaParser.TYPE_INTEGER_WRAPPER;
	import static com.android.tools.lint.client.api.JavaParser.TYPE_LONG_WRAPPER;
	import static com.android.tools.lint.detector.api.LintUtils.skipParentheses;

	import com.android.annotations.NonNull;
	import com.android.annotations.Nullable;
	import com.android.tools.lint.client.api.JavaEvaluator;
	import com.android.tools.lint.detector.api.Category;
	import com.android.tools.lint.detector.api.Detector;
	import com.android.tools.lint.detector.api.Implementation;
	import com.android.tools.lint.detector.api.Issue;
	import com.android.tools.lint.detector.api.JavaContext;
	import com.android.tools.lint.detector.api.Scope;
	import com.android.tools.lint.detector.api.Severity;
	import com.android.tools.lint.detector.api.TextFormat;
	import com.google.common.collect.Sets;
	import com.google.common.collect.Sets.SetView;
	import com.intellij.psi.JavaElementVisitor;
	import com.intellij.psi.JavaRecursiveElementVisitor;
	import com.intellij.psi.PsiAssignmentExpression;
	import com.intellij.psi.PsiBinaryExpression;
	import com.intellij.psi.PsiElement;
	import com.intellij.psi.PsiExpression;
	import com.intellij.psi.PsiIdentifier;
	import com.intellij.psi.PsiIfStatement;
	import com.intellij.psi.PsiJavaCodeReferenceElement;
	import com.intellij.psi.PsiMethod;
	import com.intellij.psi.PsiMethodCallExpression;
	import com.intellij.psi.PsiNewExpression;
	import com.intellij.psi.PsiParenthesizedExpression;
	import com.intellij.psi.PsiPrefixExpression;
	import com.intellij.psi.PsiReferenceExpression;
	import com.intellij.psi.PsiSuperExpression;
	import com.intellij.psi.PsiThisExpression;
	import com.intellij.psi.PsiThrowStatement;
	import com.intellij.psi.PsiType;
	import com.intellij.psi.util.PsiTreeUtil;

	import java.util.ArrayList;
	import java.util.Collection;
	import java.util.HashSet;
	import java.util.List;

	/**
	* Looks for performance issues in Java files, such as memory allocations during
	* drawing operations and using HashMap instead of SparseArray.
	*/
	public class JavaPerformanceDetector extends Detector implements Detector.JavaPsiScanner {

	private static final Implementation IMPLEMENTATION = new Implementation(
	JavaPerformanceDetector.class,
	Scope.JAVA_FILE_SCOPE);

	/** Allocating objects during a paint method */
	public static final Issue PAINT_ALLOC = Issue.create(
	"DrawAllocation", //$NON-NLS-1$
	"Memory allocations within drawing code",

	"You should avoid allocating objects during a drawing or layout operation. These " +
	"are called frequently, so a smooth UI can be interrupted by garbage collection " +
	"pauses caused by the object allocations.\n" +
	"\n" +
	"The way this is generally handled is to allocate the needed objects up front " +
	"and to reuse them for each drawing operation.\n" +
	"\n" +
	"Some methods allocate memory on your behalf (such as `Bitmap.create`), and these " +
	"should be handled in the same way.",

	Category.PERFORMANCE,
	9,
	Severity.WARNING,
	IMPLEMENTATION);

	/** Using HashMaps where SparseArray would be better */
	public static final Issue USE_SPARSE_ARRAY = Issue.create(
	"UseSparseArrays", //$NON-NLS-1$
	"HashMap can be replaced with SparseArray",

	"For maps where the keys are of type integer, it's typically more efficient to " +
	"use the Android `SparseArray` API. This check identifies scenarios where you might " +
	"want to consider using `SparseArray` instead of `HashMap` for better performance.\n" +
	"\n" +
	"This is particularly useful when the value types are primitives like ints, " +
	"where you can use `SparseIntArray` and avoid auto-boxing the values from `int` to " +
	"`Integer`.\n" +
	"\n" +
	"If you need to construct a `HashMap` because you need to call an API outside of " +
	"your control which requires a `Map`, you can suppress this warning using for " +
	"example the `@SuppressLint` annotation.",

	Category.PERFORMANCE,
	4,
	Severity.WARNING,
	IMPLEMENTATION);

	/** Using {@code new Integer()} instead of the more efficient {@code Integer.valueOf} */
	public static final Issue USE_VALUE_OF = Issue.create(
	"UseValueOf", //$NON-NLS-1$
	"Should use `valueOf` instead of `new`",

	"You should not call the constructor for wrapper classes directly, such as" +
	"`new Integer(42)`. Instead, call the `valueOf` factory method, such as " +
	"`Integer.valueOf(42)`. This will typically use less memory because common integers " +
	"such as 0 and 1 will share a single instance.",

	Category.PERFORMANCE,
	4,
	Severity.WARNING,
	IMPLEMENTATION);

	static final String ON_MEASURE = "onMeasure";
	static final String ON_DRAW = "onDraw";
	static final String ON_LAYOUT = "onLayout";
	private static final String LAYOUT = "layout";
	private static final String HASH_MAP = "java.util.HashMap";
	private static final String SPARSE_ARRAY = "android.util.SparseArray";
	public static final String CLASS_CANVAS = "android.graphics.Canvas";

	/** Constructs a new {@link JavaPerformanceDetector} check */
	public JavaPerformanceDetector() {
	}

	// ---- Implements JavaScanner ----

	@Override
	public List<Class<? extends PsiElement>> getApplicablePsiTypes() {
	List<Class<? extends PsiElement>> types = new ArrayList<Class<? extends PsiElement>>(3);
	types.add(PsiNewExpression.class);
	types.add(PsiMethod.class);
	types.add(PsiMethodCallExpression.class);
	return types;
	}

	@Override
	public JavaElementVisitor createPsiVisitor(@NonNull JavaContext context) {
	return new PerformanceVisitor(context);
	}

	private static class PerformanceVisitor extends JavaElementVisitor {
	private final JavaContext mContext;
	private final boolean mCheckMaps;
	private final boolean mCheckAllocations;
	private final boolean mCheckValueOf;
	/** Whether allocations should be "flagged" in the current method */
	private boolean mFlagAllocations;

	public PerformanceVisitor(JavaContext context) {
	mContext = context;

	mCheckAllocations = context.isEnabled(PAINT_ALLOC);
	mCheckMaps = context.isEnabled(USE_SPARSE_ARRAY);
	mCheckValueOf = context.isEnabled(USE_VALUE_OF);
	}

	@Override
	public void visitMethod(PsiMethod node) {
	mFlagAllocations = isBlockedAllocationMethod(node);
	}

	@Override
	public void visitNewExpression(PsiNewExpression node) {
	String typeName = null;
	PsiJavaCodeReferenceElement classReference = node.getClassReference();
	if (mCheckMaps \|\| mCheckValueOf) {
	if (classReference != null) {
	typeName = classReference.getQualifiedName();
	}
	}

	if (mCheckMaps) {
	// TODO: Should we handle factory method constructions of HashMaps as well,
	// e.g. via Guava? This is a bit trickier since we need to infer the type
	// arguments from the calling context.
	if (HASH_MAP.equals(typeName)) {
	checkHashMap(node, classReference);
	} else if (SPARSE_ARRAY.equals(typeName)) {
	checkSparseArray(node, classReference);
	}
	}

	if (mCheckValueOf) {
	if (typeName != null
	&& (typeName.equals(TYPE_INTEGER_WRAPPER)
	\|\| typeName.equals(TYPE_BOOLEAN_WRAPPER)
	\|\| typeName.equals(TYPE_FLOAT_WRAPPER)
	\|\| typeName.equals(TYPE_CHARACTER_WRAPPER)
	\|\| typeName.equals(TYPE_LONG_WRAPPER)
	\|\| typeName.equals(TYPE_DOUBLE_WRAPPER)
	\|\| typeName.equals(TYPE_BYTE_WRAPPER))
	//&& node.astTypeReference().astParts().size() == 1
	&& node.getArgumentList() != null
	&& node.getArgumentList().getExpressions().length == 1) {
	String argument = node.getArgumentList().getExpressions()[0].getText();
	mContext.report(USE_VALUE_OF, node, mContext.getLocation(node), getUseValueOfErrorMessage(
	typeName, argument));
	}
	}

	if (mFlagAllocations
	&& !(skipParentheses(node.getParent()) instanceof PsiThrowStatement)
	&& mCheckAllocations) {
	// Make sure we're still inside the method declaration that marked
	// mInDraw as true, in case we've left it and we're in a static
	// block or something:
	PsiMethod method = PsiTreeUtil.getParentOfType(node, PsiMethod.class);
	if (method != null && isBlockedAllocationMethod(method)
	&& !isLazilyInitialized(node)) {
	reportAllocation(node);
	}
	}
	}

	private void reportAllocation(PsiElement node) {
	mContext.report(PAINT_ALLOC, node, mContext.getLocation(node),
	"Avoid object allocations during draw/layout operations (preallocate and " +
	"reuse instead)");
	}

	@Override
	public void visitMethodCallExpression(PsiMethodCallExpression node) {
	if (!mFlagAllocations) {
	return;
	}
	PsiReferenceExpression expression = node.getMethodExpression();
	PsiElement qualifier = expression.getQualifier();
	if (qualifier == null) {
	return;
	}
	String methodName = expression.getReferenceName();
	if (methodName == null) {
	return;
	}
	// Look for forbidden methods
	if (methodName.equals("createBitmap") //$NON-NLS-1$
	\|\| methodName.equals("createScaledBitmap")) { //$NON-NLS-1$
	PsiMethod method = node.resolveMethod();
	if (method != null && mContext.getEvaluator().isMemberInClass(method,
	"android.graphics.Bitmap") && !isLazilyInitialized(node)) {
	reportAllocation(node);
	}
	} else if (methodName.startsWith("decode")) { //$NON-NLS-1$
	// decodeFile, decodeByteArray, ...
	PsiMethod method = node.resolveMethod();
	if (method != null && mContext.getEvaluator().isMemberInClass(method,
	"android.graphics.BitmapFactory") && !isLazilyInitialized(node)) {
	reportAllocation(node);
	}
	} else if (methodName.equals("getClipBounds")) { //$NON-NLS-1$
	if (node.getArgumentList().getExpressions().length == 0) {
	mContext.report(PAINT_ALLOC, node, mContext.getLocation(node),
	"Avoid object allocations during draw operations: Use " +
	"`Canvas.getClipBounds(Rect)` instead of `Canvas.getClipBounds()` " +
	"which allocates a temporary `Rect`");
	}
	}
	}

	/**
	* Check whether the given invocation is done as a lazy initialization,
	* e.g. {@code if (foo == null) foo = new Foo();}.
	* <p>
	* This tries to also handle the scenario where the check is on some
	* <b>other</b> variable - e.g.
	* <pre>
	* if (foo == null) {
	* foo == init1();
	* bar = new Bar();
	* }
	* </pre>
	* or
	* <pre>
	* if (!initialized) {
	* initialized = true;
	* bar = new Bar();
	* }
	* </pre>
	*/
	private static boolean isLazilyInitialized(PsiElement node) {
	PsiElement curr = node.getParent();
	while (curr != null) {
	if (curr instanceof PsiMethod) {
	return false;
	} else if (curr instanceof PsiIfStatement) {
	PsiIfStatement ifNode = (PsiIfStatement) curr;
	// See if the if block represents a lazy initialization:
	// compute all variable names seen in the condition
	// (e.g. for "if (foo == null \|\| bar != foo)" the result is "foo,bar"),
	// and then compute all variables assigned to in the if body,
	// and if there is an overlap, we'll consider the whole if block
	// guarded (so lazily initialized and an allocation we won't complain
	// about.)
	List<String> assignments = new ArrayList<String>();
	AssignmentTracker visitor = new AssignmentTracker(assignments);
	if (ifNode.getThenBranch() != null) {
	ifNode.getThenBranch().accept(visitor);
	}
	if (!assignments.isEmpty()) {
	List<String> references = new ArrayList<String>();
	addReferencedVariables(references, ifNode.getCondition());
	if (!references.isEmpty()) {
	SetView<String> intersection = Sets.intersection(
	new HashSet<String>(assignments),
	new HashSet<String>(references));
	return !intersection.isEmpty();
	}
	}
	return false;

	}
	curr = curr.getParent();
	}

	return false;
	}

	/** Adds any variables referenced in the given expression into the given list */
	private static void addReferencedVariables(
	@NonNull Collection<String> variables,
	@Nullable PsiExpression expression) {
	if (expression instanceof PsiBinaryExpression) {
	PsiBinaryExpression binary = (PsiBinaryExpression) expression;
	addReferencedVariables(variables, binary.getLOperand());
	addReferencedVariables(variables, binary.getROperand());
	} else if (expression instanceof PsiPrefixExpression) {
	PsiPrefixExpression unary = (PsiPrefixExpression) expression;
	addReferencedVariables(variables, unary.getOperand());
	} else if (expression instanceof PsiParenthesizedExpression) {
	PsiParenthesizedExpression exp = (PsiParenthesizedExpression) expression;
	addReferencedVariables(variables, exp.getExpression());
	} else if (expression instanceof PsiIdentifier) {
	PsiIdentifier reference = (PsiIdentifier) expression;
	variables.add(reference.getText());
	} else if (expression instanceof PsiReferenceExpression) {
	PsiReferenceExpression ref = (PsiReferenceExpression) expression;
	PsiElement qualifier = ref.getQualifier();
	if (qualifier != null) {
	if (qualifier instanceof PsiThisExpression \|\|
	qualifier instanceof PsiSuperExpression) {
	variables.add(ref.getReferenceName());
	}
	} else {
	variables.add(ref.getReferenceName());
	}
	}
	}

	/**
	* Returns whether the given method declaration represents a method
	* where allocating objects is not allowed for performance reasons
	*/
	private boolean isBlockedAllocationMethod(
	@NonNull PsiMethod node) {
	JavaEvaluator evaluator = mContext.getEvaluator();
	return isOnDrawMethod(evaluator, node)
	\|\| isOnMeasureMethod(evaluator, node)
	\|\| isOnLayoutMethod(evaluator, node)
	\|\| isLayoutMethod(evaluator, node);
	}

	/**
	* Returns true if this method looks like it's overriding android.view.View's
	* {@code protected void onDraw(Canvas canvas)}
	*/
	private static boolean isOnDrawMethod(
	@NonNull JavaEvaluator evaluator,
	@NonNull PsiMethod node) {
	return ON_DRAW.equals(node.getName()) && evaluator.parametersMatch(node, CLASS_CANVAS);
	}

	/**
	* Returns true if this method looks like it's overriding
	* android.view.View's
	* {@code protected void onLayout(boolean changed, int left, int top,
	* int right, int bottom)}
	*/
	private static boolean isOnLayoutMethod(
	@NonNull JavaEvaluator evaluator,
	@NonNull PsiMethod node) {
	return ON_LAYOUT.equals(node.getName()) && evaluator.parametersMatch(node,
	TYPE_BOOLEAN, TYPE_INT, TYPE_INT, TYPE_INT, TYPE_INT);
	}

	/**
	* Returns true if this method looks like it's overriding android.view.View's
	* {@code protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)}
	*/
	private static boolean isOnMeasureMethod(
	@NonNull JavaEvaluator evaluator,
	@NonNull PsiMethod node) {
	return ON_MEASURE.equals(node.getName()) && evaluator.parametersMatch(node,
	TYPE_INT, TYPE_INT);
	}

	/**
	* Returns true if this method looks like it's overriding android.view.View's
	* {@code public void layout(int l, int t, int r, int b)}
	*/
	private static boolean isLayoutMethod(
	@NonNull JavaEvaluator evaluator,
	@NonNull PsiMethod node) {
	return LAYOUT.equals(node.getName()) && evaluator.parametersMatch(node,
	TYPE_INT, TYPE_INT, TYPE_INT, TYPE_INT);
	}

	/**
	* Checks whether the given constructor call and type reference refers
	* to a HashMap constructor call that is eligible for replacement by a
	* SparseArray call instead
	*/
	private void checkHashMap(
	@NonNull PsiNewExpression node,
	@NonNull PsiJavaCodeReferenceElement reference) {
	PsiType[] types = reference.getTypeParameters();
	if (types.length == 2) {
	PsiType first = types[0];
	String typeName = first.getCanonicalText();
	int minSdk = mContext.getMainProject().getMinSdk();
	if (TYPE_INTEGER_WRAPPER.equals(typeName) \|\| TYPE_BYTE_WRAPPER.equals(typeName)) {
	String valueType = types[1].getCanonicalText();
	if (valueType.equals(TYPE_INTEGER_WRAPPER)) {
	mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
	"Use new `SparseIntArray(...)` instead for better performance");
	} else if (valueType.equals(TYPE_LONG_WRAPPER) && minSdk >= 18) {
	mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
	"Use `new SparseLongArray(...)` instead for better performance");
	} else if (valueType.equals(TYPE_BOOLEAN_WRAPPER)) {
	mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
	"Use `new SparseBooleanArray(...)` instead for better performance");
	} else {
	mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
	String.format(
	"Use `new SparseArray<%1$s>(...)` instead for better performance",
	valueType.substring(valueType.lastIndexOf('.') + 1)));
	}
	} else if (TYPE_LONG_WRAPPER.equals(typeName) && (minSdk >= 16 \|\|
	Boolean.TRUE == mContext.getMainProject().dependsOn(
	SUPPORT_LIB_ARTIFACT))) {
	boolean useBuiltin = minSdk >= 16;
	String message = useBuiltin ?
	"Use `new LongSparseArray(...)` instead for better performance" :
	"Use `new android.support.v4.util.LongSparseArray(...)` instead for better performance";
	mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
	message);
	}
	}
	}

	private void checkSparseArray(
	@NonNull PsiNewExpression node,
	@NonNull PsiJavaCodeReferenceElement reference) {
	PsiType[] types = reference.getTypeParameters();
	if (types.length == 1) {
	String valueType = types[0].getCanonicalText();
	if (valueType.equals(TYPE_INTEGER_WRAPPER)) {
	mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
	"Use `new SparseIntArray(...)` instead for better performance");
	} else if (valueType.equals(TYPE_BOOLEAN_WRAPPER)) {
	mContext.report(USE_SPARSE_ARRAY, node, mContext.getLocation(node),
	"Use `new SparseBooleanArray(...)` instead for better performance");
	}
	}
	}
	}

	private static String getUseValueOfErrorMessage(String typeName, String argument) {
	// Keep in sync with {@link #getReplacedType} below
	return String.format("Use `%1$s.valueOf(%2$s)` instead",
	typeName.substring(typeName.lastIndexOf('.') + 1), argument);
	}

	/**
	* For an error message for an {@link #USE_VALUE_OF} issue reported by this detector,
	* returns the type being replaced. Intended to use for IDE quickfix implementations.
	*/
	@SuppressWarnings("unused") // Used by the IDE
	@Nullable
	public static String getReplacedType(@NonNull String message, @NonNull TextFormat format) {
	message = format.toText(message);
	int index = message.indexOf('.');
	if (index != -1 && message.startsWith("Use ")) {
	return message.substring(4, index);
	}
	return null;
	}

	/** Visitor which records variable names assigned into */
	private static class AssignmentTracker extends JavaRecursiveElementVisitor {
	private final Collection<String> mVariables;

	public AssignmentTracker(Collection<String> variables) {
	mVariables = variables;
	}

	@Override
	public void visitAssignmentExpression(PsiAssignmentExpression node) {
	super.visitAssignmentExpression(node);

	PsiExpression left = node.getLExpression();
	if (left instanceof PsiReferenceExpression) {
	PsiReferenceExpression ref = (PsiReferenceExpression) left;
	if (ref.getQualifier() instanceof PsiThisExpression \|\|
	ref.getQualifier() instanceof PsiSuperExpression) {
	mVariables.add(ref.getReferenceName());
	} else {
	mVariables.add(ref.getText());
	}
	} else if (left instanceof PsiIdentifier) {
	mVariables.add(left.getText());
	}
	}
	}
	}