com.google.common.base.CaseFormat.java Source code

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/*
 * 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();
    }
}