maven-jxr/src/main/java/org/apache/maven/jxr/util/SimpleWordTokenizer.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.maven.jxr.util;

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

/**
 * This is a small and fast word tokenizer. It has different characteristics from the normal Java tokenizer. It only
 * considers clear words that are only ended with spaces as strings. EX: "Flight" would be a word but "Flight()" would
 * not.
 */
public class SimpleWordTokenizer {

    private static final Pattern NONBREAKERS = Pattern.compile("([^()\\[ {}]+)");

    private static final char[] BREAKERS = {'(', ')', '[', ' ', '{', '}'};

    /**
     * Breaks the given line into multiple tokens.
     *
     * @param line line to tokenize
     * @return list of tokens
     */
    public static List<StringEntry> tokenize(String line) {

        /*
         * determine where to start processing this String... this could either be the start of the line or just keep
         * going until the first
         */
        int start = getStart(line);

        // find the first non-BREAKER char and assume that is where you want to start

        if (line == null || line.length() == 0 || start == -1) {
            return Collections.emptyList();
        }

        return tokenize(line, start);
    }

    /**
     * Tokenize the given line but only return those tokens that match the parameter {@code find}.
     *
     * @param line line to search in
     * @param find String to match
     * @return list of matching tokens
     */
    public static List<StringEntry> tokenize(String line, String find) {

        List<StringEntry> foundTokens = new ArrayList<>();

        for (StringEntry se : tokenize(line)) {

            if (se.toString().equals(find)) {
                foundTokens.add(se);
            }
        }

        return foundTokens;
    }

    /**
     * Internal impl. Specify the start and end.
     */
    private static List<StringEntry> tokenize(String line, int start) {
        Matcher matcher = NONBREAKERS.matcher(line.substring(start));

        List<StringEntry> words = new ArrayList<>();

        while (matcher.find()) {
            StringEntry entry = new StringEntry(matcher.group(1), matcher.start() + start);
            words.add(entry);
        }

        return words;
    }

    /**
     * Go through the list of BREAKERS and find the closes one.
     */
    private static int getStart(String string) {

        for (int i = 0; i < string.length(); ++i) {

            if (!isBreaker(string.charAt(i))) {
                return i;
            }
        }

        return -1;
    }

    /**
     * Return true if the given char is considered a breaker.
     */
    private static boolean isBreaker(char c) {

        for (char breaker : BREAKERS) {

            if (breaker == c) {
                return true;
            }
        }

        return false;
    }
}