Java tutorial
/* * Copyright (C) 2006 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 static com.google.common.base.Preconditions.checkNotNull; import com.google.common.annotations.Beta; import com.google.common.annotations.GwtCompatible; import java.io.Serializable; import javax.annotation.CheckReturnValue; import javax.annotation.Nullable; /** * Utility class for converting between various ASCII case formats. Behavior is undefined for * non-ASCII input. * * @author Mike Bostock * @since 1.0 */ @CheckReturnValue @GwtCompatible public enum CaseFormat { /** * Hyphenated variable naming convention, e.g., "lower-hyphen". */ LOWER_HYPHEN(CharMatcher.is('-'), "-") { @Override String normalizeWord(String word) { return Ascii.toLowerCase(word); } @Override String convert(CaseFormat format, String s) { if (format == LOWER_UNDERSCORE) { return s.replace('-', '_'); } if (format == UPPER_UNDERSCORE) { return Ascii.toUpperCase(s.replace('-', '_')); } return super.convert(format, s); } }, /** * C++ variable naming convention, e.g., "lower_underscore". */ LOWER_UNDERSCORE(CharMatcher.is('_'), "_") { @Override String normalizeWord(String word) { return Ascii.toLowerCase(word); } @Override String convert(CaseFormat format, String s) { if (format == LOWER_HYPHEN) { return s.replace('_', '-'); } if (format == UPPER_UNDERSCORE) { return Ascii.toUpperCase(s); } return super.convert(format, s); } }, /** * Java variable naming convention, e.g., "lowerCamel". */ LOWER_CAMEL(CharMatcher.inRange('A', 'Z'), "") { @Override String normalizeWord(String word) { return firstCharOnlyToUpper(word); } }, /** * Java and C++ class naming convention, e.g., "UpperCamel". */ UPPER_CAMEL(CharMatcher.inRange('A', 'Z'), "") { @Override String normalizeWord(String word) { return firstCharOnlyToUpper(word); } }, /** * Java and C++ constant naming convention, e.g., "UPPER_UNDERSCORE". */ UPPER_UNDERSCORE(CharMatcher.is('_'), "_") { @Override String normalizeWord(String word) { return Ascii.toUpperCase(word); } @Override String convert(CaseFormat format, String s) { if (format == LOWER_HYPHEN) { return Ascii.toLowerCase(s.replace('_', '-')); } if (format == LOWER_UNDERSCORE) { return Ascii.toLowerCase(s); } return super.convert(format, s); } }; private final CharMatcher wordBoundary; private final String wordSeparator; CaseFormat(CharMatcher wordBoundary, String wordSeparator) { this.wordBoundary = wordBoundary; this.wordSeparator = wordSeparator; } /** * Converts the specified {@code String str} from this format to the specified {@code format}. A * "best effort" approach is taken; if {@code str} does not conform to the assumed format, then * the behavior of this method is undefined but we make a reasonable effort at converting anyway. */ public final String to(CaseFormat format, String str) { checkNotNull(format); checkNotNull(str); return (format == this) ? str : convert(format, str); } /** * Enum values can override for performance reasons. */ String convert(CaseFormat format, String s) { // deal with camel conversion StringBuilder out = null; int i = 0; int j = -1; while ((j = wordBoundary.indexIn(s, ++j)) != -1) { if (i == 0) { // include some extra space for separators out = new StringBuilder(s.length() + 4 * wordSeparator.length()); out.append(format.normalizeFirstWord(s.substring(i, j))); } else { out.append(format.normalizeWord(s.substring(i, j))); } out.append(format.wordSeparator); i = j + wordSeparator.length(); } return (i == 0) ? format.normalizeFirstWord(s) : out.append(format.normalizeWord(s.substring(i))).toString(); } /** * Returns a {@code Converter} that converts strings from this format to {@code targetFormat}. * * @since 16.0 */ @Beta public Converter<String, String> converterTo(CaseFormat targetFormat) { return new StringConverter(this, targetFormat); } private static final class StringConverter extends Converter<String, String> implements Serializable { private final CaseFormat sourceFormat; private final CaseFormat targetFormat; StringConverter(CaseFormat sourceFormat, CaseFormat targetFormat) { this.sourceFormat = checkNotNull(sourceFormat); this.targetFormat = checkNotNull(targetFormat); } @Override protected String doForward(String s) { return sourceFormat.to(targetFormat, s); } @Override protected String doBackward(String s) { return targetFormat.to(sourceFormat, s); } @Override public boolean equals(@Nullable Object object) { if (object instanceof StringConverter) { StringConverter that = (StringConverter) object; return sourceFormat.equals(that.sourceFormat) && targetFormat.equals(that.targetFormat); } return false; } @Override public int hashCode() { return sourceFormat.hashCode() ^ targetFormat.hashCode(); } @Override public String toString() { return sourceFormat + ".converterTo(" + targetFormat + ")"; } private static final long serialVersionUID = 0L; } abstract String normalizeWord(String word); private String normalizeFirstWord(String word) { return (this == LOWER_CAMEL) ? Ascii.toLowerCase(word) : normalizeWord(word); } private static String firstCharOnlyToUpper(String word) { return (word.isEmpty()) ? word : new StringBuilder(word.length()).append(Ascii.toUpperCase(word.charAt(0))) .append(Ascii.toLowerCase(word.substring(1))).toString(); } }