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/*
* Copyright (C) 2009 The Guava Authors
*
* 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.google.common.base;
import com.google.common.annotations.GwtCompatible;
import java.lang.ref.WeakReference;
import java.util.Locale;
import java.util.ServiceConfigurationError;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.regex.Pattern;
import javax.annotation.CheckForNull;
/**
* Methods factored out so that they can be emulated differently in GWT.
*
* @author Jesse Wilson
*/
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
final class Platform {
private static final Logger logger = Logger.getLogger(Platform.class.getName());
private static final PatternCompiler patternCompiler = loadPatternCompiler();
private Platform() {}
static CharMatcher precomputeCharMatcher(CharMatcher matcher) {
return matcher.precomputedInternal();
}
static <T extends Enum<T>> Optional<T> getEnumIfPresent(Class<T> enumClass, String value) {
WeakReference<? extends Enum<?>> ref = Enums.getEnumConstants(enumClass).get(value);
return ref == null ? Optional.<T>absent() : Optional.of(enumClass.cast(ref.get()));
}
static String formatCompact4Digits(double value) {
return String.format(Locale.ROOT, "%.4g", value);
}
static boolean stringIsNullOrEmpty(@CheckForNull String string) {
return string == null || string.isEmpty();
}
/**
* Returns the string if it is not null, or an empty string otherwise.
*
* @param string the string to test and possibly return
* @return {@code string} if it is not null; {@code ""} otherwise
*/
static String nullToEmpty(@CheckForNull String string) {
return (string == null) ? "" : string;
}
/**
* Returns the string if it is not empty, or a null string otherwise.
*
* @param string the string to test and possibly return
* @return {@code string} if it is not empty; {@code null} otherwise
*/
@CheckForNull
static String emptyToNull(@CheckForNull String string) {
return stringIsNullOrEmpty(string) ? null : string;
}
static CommonPattern compilePattern(String pattern) {
Preconditions.checkNotNull(pattern);
return patternCompiler.compile(pattern);
}
static boolean patternCompilerIsPcreLike() {
return patternCompiler.isPcreLike();
}
private static PatternCompiler loadPatternCompiler() {
/*
* We'd normally use ServiceLoader here, but it hurts Android startup performance. To avoid
* that, we hardcode the JDK Pattern compiler on Android (and, inadvertently, on App Engine and
* in Guava, at least for now).
*/
return new JdkPatternCompiler();
}
private static void logPatternCompilerError(ServiceConfigurationError e) {
logger.log(Level.WARNING, "Error loading regex compiler, falling back to next option", e);
}
private static final class JdkPatternCompiler implements PatternCompiler {
@Override
public CommonPattern compile(String pattern) {
return new JdkPattern(Pattern.compile(pattern));
}
@Override
public boolean isPcreLike() {
return true;
}
}
}
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