ParsingUtils.java

/*
 * Copyright 2014 the original author or 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 org.springframework.data.util;

import lombok.experimental.UtilityClass;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.regex.Pattern;

import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Utility methods for {@link String} parsing.
 * 
 * @author Oliver Gierke
 * @since 1.5
 */
@UtilityClass
public class ParsingUtils {

	private static final String UPPER = "\\p{Lu}|\\P{InBASIC_LATIN}";
	private static final String LOWER = "\\p{Ll}";
	private static final String CAMEL_CASE_REGEX = "(?<!(^|[%u_$]))(?=[%u])|(?<!^)(?=[%u][%l])". //
			replace("%u", UPPER).replace("%l", LOWER);

	private static final Pattern CAMEL_CASE = Pattern.compile(CAMEL_CASE_REGEX);

	/**
	 * Splits up the given camel-case {@link String}.
	 * 
	 * @param source must not be {@literal null}.
	 * @return
	 */
	public static List<String> splitCamelCase(String source) {
		return split(source, false);
	}

	/**
	 * Splits up the given camel-case {@link String} and returns the parts in lower case.
	 * 
	 * @param source must not be {@literal null}.
	 * @return
	 */
	public static List<String> splitCamelCaseToLower(String source) {
		return split(source, true);
	}

	/**
	 * Reconcatenates the given camel-case source {@link String} using the given delimiter. Will split up the camel-case
	 * {@link String} and use an uncapitalized version of the parts.
	 * 
	 * @param source must not be {@literal null}.
	 * @param delimiter must not be {@literal null}.
	 * @return
	 */
	public static String reconcatenateCamelCase(String source, String delimiter) {

		Assert.notNull(source, "Source string must not be null!");
		Assert.notNull(delimiter, "Delimiter must not be null!");

		return StringUtils.collectionToDelimitedString(splitCamelCaseToLower(source), delimiter);
	}

	private static List<String> split(String source, boolean toLower) {

		Assert.notNull(source, "Source string must not be null!");

		String[] parts = CAMEL_CASE.split(source);
		List<String> result = new ArrayList<>(parts.length);

		for (String part : parts) {
			result.add(toLower ? part.toLowerCase() : part);
		}

		return Collections.unmodifiableList(result);
	}
}