/*
 * 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.Iterator;
import java.util.Locale;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.regex.Pattern;
import org.checkerframework.checker.nullness.qual.Nullable;

Methods factored out so that they can be emulated differently in GWT.
Author:Jesse Wilson
/** * Methods factored out so that they can be emulated differently in GWT. * * @author Jesse Wilson */
@GwtCompatible(emulated = true) final class Platform { private static final Logger logger = Logger.getLogger(Platform.class.getName()); private static final PatternCompiler patternCompiler = loadPatternCompiler(); private Platform() {} /** Calls {@link System#nanoTime()}. */ static long systemNanoTime() { return System.nanoTime(); } 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(@Nullable String string) { return string == null || string.isEmpty(); } static String nullToEmpty(@Nullable String string) { return (string == null) ? "" : string; } static String emptyToNull(@Nullable String string) { return stringIsNullOrEmpty(string) ? null : string; } static CommonPattern compilePattern(String pattern) { Preconditions.checkNotNull(pattern); return patternCompiler.compile(pattern); } static boolean usingJdkPatternCompiler() { return patternCompiler instanceof JdkPatternCompiler; } private static PatternCompiler loadPatternCompiler() { ServiceLoader<PatternCompiler> loader = ServiceLoader.load(PatternCompiler.class); // Returns the first PatternCompiler that loads successfully. try { for (Iterator<PatternCompiler> it = loader.iterator(); it.hasNext(); ) { try { return it.next(); } catch (ServiceConfigurationError e) { logPatternCompilerError(e); } } } catch (ServiceConfigurationError e) { // from hasNext() logPatternCompilerError(e); } // Fall back to the JDK regex library. 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)); } } }