Java String Split split(String str)

Description

Split a string using the default separator

License

Apache License

Parameter

Parameter	Description
str	a string that may have escaped separator

Return

an array of strings

Declaration

public static String[] split(String str) 

Method Source Code

//package com.java2s;
/**/*from  w  w w. ja  v a2  s .c om*/
 * 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.
 */

import java.util.ArrayList;

public class Main {
    final public static char COMMA = ',';
    final public static char ESCAPE_CHAR = '\\';

    /**
     * Split a string using the default separator
     * @param str a string that may have escaped separator
     * @return an array of strings
     */
    public static String[] split(String str) {
        return split(str, ESCAPE_CHAR, COMMA);
    }

    /**
     * Split a string using the given separator
     * @param str a string that may have escaped separator
     * @param escapeChar a char that be used to escape the separator
     * @param separator a separator char
     * @return an array of strings
     */
    public static String[] split(String str, char escapeChar, char separator) {
        if (str == null) {
            return null;
        }
        ArrayList<String> strList = new ArrayList<String>();
        StringBuilder split = new StringBuilder();
        int index = 0;
        while ((index = findNext(str, separator, escapeChar, index, split)) >= 0) {
            ++index; // move over the separator for next search
            strList.add(split.toString());
            split.setLength(0); // reset the buffer
        }
        strList.add(split.toString());
        // remove trailing empty split(s)
        int last = strList.size(); // last split
        while (--last >= 0 && "".equals(strList.get(last))) {
            strList.remove(last);
        }
        return strList.toArray(new String[strList.size()]);
    }

    /**
     * Split a string using the given separator, with no escaping performed.
     * @param str a string to be split. Note that this may not be null.
     * @param separator a separator char
     * @return an array of strings
     */
    public static String[] split(String str, char separator) {
        // String.split returns a single empty result for splitting the empty
        // string.
        if (str.isEmpty()) {
            return new String[] { "" };
        }
        ArrayList<String> strList = new ArrayList<String>();
        int startIndex = 0;
        int nextIndex = 0;
        while ((nextIndex = str.indexOf(separator, startIndex)) != -1) {
            strList.add(str.substring(startIndex, nextIndex));
            startIndex = nextIndex + 1;
        }
        strList.add(str.substring(startIndex));
        // remove trailing empty split(s)
        int last = strList.size(); // last split
        while (--last >= 0 && "".equals(strList.get(last))) {
            strList.remove(last);
        }
        return strList.toArray(new String[strList.size()]);
    }

    /**
     * Finds the first occurrence of the separator character ignoring the escaped
     * separators starting from the index. Note the substring between the index
     * and the position of the separator is passed.
     * @param str the source string
     * @param separator the character to find
     * @param escapeChar character used to escape
     * @param start from where to search
     * @param split used to pass back the extracted string
     */
    public static int findNext(String str, char separator, char escapeChar, int start, StringBuilder split) {
        int numPreEscapes = 0;
        for (int i = start; i < str.length(); i++) {
            char curChar = str.charAt(i);
            if (numPreEscapes == 0 && curChar == separator) { // separator
                return i;
            } else {
                split.append(curChar);
                numPreEscapes = (curChar == escapeChar) ? (++numPreEscapes) % 2 : 0;
            }
        }
        return -1;
    }
}

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