com.android.tools.lint.checks.MathDetector Maven / Gradle / Ivy
/*
* Copyright (C) 2011 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 com.android.annotations.NonNull;
import com.android.annotations.Nullable;
import com.android.tools.lint.client.api.JavaParser.ResolvedMethod;
import com.android.tools.lint.client.api.JavaParser.ResolvedNode;
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.Location;
import com.android.tools.lint.detector.api.Scope;
import com.android.tools.lint.detector.api.Severity;
import java.util.Arrays;
import java.util.List;
import lombok.ast.AstVisitor;
import lombok.ast.Expression;
import lombok.ast.MethodInvocation;
/**
* Looks for usages of {@link java.lang.Math} methods which can be replaced with
* {@code android.util.FloatMath} methods to avoid casting.
*/
public class MathDetector extends Detector implements Detector.JavaScanner {
/** The main issue discovered by this detector */
public static final Issue ISSUE = Issue.create(
"FloatMath", //$NON-NLS-1$
"Using `FloatMath` instead of `Math`",
"In older versions of Android, using `android.util.FloatMath` was recommended " +
"for performance reasons when operating on floats. However, on modern hardware " +
"doubles are just as fast as float (though they take more memory), and in " +
"recent versions of Android, `FloatMath` is actually slower than using `java.lang.Math` " +
"due to the way the JIT optimizes `java.lang.Math`. Therefore, you should use " +
"`Math` instead of `FloatMath` if you are only targeting Froyo and above.",
Category.PERFORMANCE,
3,
Severity.WARNING,
new Implementation(
MathDetector.class,
Scope.JAVA_FILE_SCOPE))
.addMoreInfo(
"http://developer.android.com/guide/practices/design/performance.html#avoidfloat"); //$NON-NLS-1$
/** Constructs a new {@link MathDetector} check */
public MathDetector() {
}
// ---- Implements JavaScanner ----
@Nullable
@Override
public List getApplicableMethodNames() {
return Arrays.asList(
"sin", //$NON-NLS-1$
"cos", //$NON-NLS-1$
"ceil", //$NON-NLS-1$
"sqrt", //$NON-NLS-1$
"floor" //$NON-NLS-1$
);
}
@Override
public void visitMethod(@NonNull JavaContext context, @Nullable AstVisitor visitor,
@NonNull MethodInvocation call) {
Expression operand = call.astOperand();
if (operand == null || !operand.toString().equals("Math")) {
ResolvedNode resolved = context.resolve(call);
if (resolved instanceof ResolvedMethod &&
((ResolvedMethod)resolved).getContainingClass().matches("android.util.FloatMath")
&& context.getProject().getMinSdk() >= 8) {
String message = String.format(
"Use `java.lang.Math#%1$s` instead of `android.util.FloatMath#%1$s()` " +
"since it is faster as of API 8", call.astName().astValue());
Location location = operand != null
? context.getRangeLocation(operand, 0, call.astName(), 0)
: context.getLocation(call);
context.report(ISSUE, call, location, message);
}
}
}
}