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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LANG-1124) Add split by length methods in StringUtils
Date Sat, 16 May 2015 13:21:00 GMT

    [ https://issues.apache.org/jira/browse/LANG-1124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14546744#comment-14546744
] 

ASF GitHub Bot commented on LANG-1124:
--------------------------------------

Github user rikles commented on a diff in the pull request:

    https://github.com/apache/commons-lang/pull/75#discussion_r30461086
  
    --- Diff: src/main/java/org/apache/commons/lang3/StringUtils.java ---
    @@ -3277,6 +3277,164 @@ public static String substringBetween(final String str, final
String open, final
             return list.toArray(new String[list.size()]);
         }
     
    +    /**
    +     * <p>Split a String into an array, using an array of fixed string lengths.</p>
    +     *
    +     * <p>If not null String input, the returned array size is same as the input
lengths array.</p>
    +     *
    +     * <p>A null input String returns {@code null}.
    +     * A {@code null} or empty input lengths array returns an empty array.
    +     * A {@code 0} in the input lengths array results in en empty string.</p>
    +     *
    +     * <p>Extra characters are ignored (ie String length greater than sum of split
lengths).
    +     * All empty substrings other than zero length requested, are returned {@code null}.</p>
    +     *
    +     * <pre>
    +     * StringUtils.splitByLength(null, *)      = null
    +     * StringUtils.splitByLength("abc")        = []
    +     * StringUtils.splitByLength("abc", null)  = []
    +     * StringUtils.splitByLength("abc", [])    = []
    +     * StringUtils.splitByLength("", 2, 4, 1)  = [null, null, null]
    +     *
    +     * StringUtils.splitByLength("abcdefg", 2, 4, 1)     = ["ab", "cdef", "g"]
    +     * StringUtils.splitByLength("abcdefghij", 2, 4, 1)  = ["ab", "cdef", "g"]
    +     * StringUtils.splitByLength("abcdefg", 2, 4, 5)     = ["ab", "cdef", "g"]
    +     * StringUtils.splitByLength("abcdef", 2, 4, 1)      = ["ab", "cdef", null]
    --- End diff --
    
    Good point.
    My idea was to indicate that there is no more characters to extract the explicitly requested
column length text.
    But in the other hand, this can cause `NullPointerException` if the returned array is
used without check...
    
    Why I used this approach : with `null` values, in case of hard coded lengths, we can simply
check the returned array with a _for each_ loop, even later in other piece of code :
    ```java
    String[] cols = StringUtils.splitByLength(input, 2, 3, 1);
    // ...
    for (String col : cols) {
        if (col == null) {
            break;
        }
        // Do something
    }
    ```
    
    Without `null` values, we must have a lengths array reference :
    ```java
    int[] LENGTHS = { 2, 3, 0, 1 };
    String[] cols = StringUtils.splitByLength(input, LENGTHS);
    int index = 0;
    for (String col : cols) {
        if (col.length() == 0 && LENGTHS[index] > 0) {
            break;
        }
        index++;
        // Do something
    }
    ```
    
    Of course, we can also check the input string length before calling `StringUtils.splitByLength`,
but we have to get the lengths sum. And what about this case : `StringUtils.splitByLength("abcd",
1, 2, 2)` ?
    
    I don't know which is best... What do you think ?


> Add split by length methods in StringUtils
> ------------------------------------------
>
>                 Key: LANG-1124
>                 URL: https://issues.apache.org/jira/browse/LANG-1124
>             Project: Commons Lang
>          Issue Type: New Feature
>          Components: lang.*
>            Reporter: Loic Guibert
>
> Add methods to split a String by fixed lengths :
> {code:java}
> public static String[] splitByLength(String str, int ... lengths);
> public static String[] splitByLengthRepeatedly(String str, int ... lengths);
> {code}
> Detail :
> {code:java}
> /**
>  * <p>Split a String into an array, using an array of fixed string lengths.</p>
>  *
>  * <p>If not null String input, the returned array size is same as the input lengths
array.</p>
>  *
>  * <p>A null input String returns {@code null}.
>  * A {@code null} or empty input lengths array returns an empty array.
>  * A {@code 0} in the input lengths array results in en empty string.</p>
>  *
>  * <p>Extra characters are ignored (ie String length greater than sum of split
lengths).
>  * All empty substrings other than zero length requested, are returned {@code null}.</p>
>  *
>  * <pre>
>  * StringUtils.splitByLength(null, *)      = null
>  * StringUtils.splitByLength("abc")        = []
>  * StringUtils.splitByLength("abc", null)  = []
>  * StringUtils.splitByLength("abc", [])    = []
>  * StringUtils.splitByLength("", 2, 4, 1)  = [null, null, null]
>  *
>  * StringUtils.splitByLength("abcdefg", 2, 4, 1)     = ["ab", "cdef", "g"]
>  * StringUtils.splitByLength("abcdefghij", 2, 4, 1)  = ["ab", "cdef", "g"]
>  * StringUtils.splitByLength("abcdefg", 2, 4, 5)     = ["ab", "cdef", "g"]
>  * StringUtils.splitByLength("abcdef", 2, 4, 1)      = ["ab", "cdef", null]
>  *
>  * StringUtils.splitByLength(" abcdef", 2, 4, 1)     = [" a", "bcde", "f"]
>  * StringUtils.splitByLength("abcdef ", 2, 4, 1)     = ["ab", "cdef", " "]
>  * StringUtils.splitByLength("abcdefg", 2, 4, 0, 1)  = ["ab", "cdef", "", "g"]
>  * StringUtils.splitByLength("abcdefg", -1)          = {@link IllegalArgumentException}
>  * </pre>
>  *
>  * @param str  the String to parse, may be null
>  * @param lengths  the string lengths where to cut, may be null, must not be negative
>  * @return an array of splitted Strings, {@code null} if null String input
>  * @throws IllegalArgumentException
>  *             if one of the lengths is negative
>  */
> public static String[] splitByLength(String str, int ... lengths);
> /**
>  * <p>Split a String into an array, using an array of fixed string lengths repeated
as
>  * many times as necessary to reach the String end.</p>
>  *
>  * <p>If not null String input, the returned array size is a multiple of the input
lengths array.</p>
>  *
>  * <p>A null input String returns {@code null}.
>  * A {@code null} or empty input lengths array returns an empty array.
>  * A {@code 0} in the input lengths array results in en empty string.</p>
>  *
>  * <p>All empty substrings other than zero length requested and following substrings,
>  * are returned {@code null}.</p>
>  *
>  * <pre>
>  * StringUtils.splitByLengthRepeated(null, *)      = null
>  * StringUtils.splitByLengthRepeated("abc")        = []
>  * StringUtils.splitByLengthRepeated("abc", null)  = []
>  * StringUtils.splitByLengthRepeated("abc", [])    = []
>  * StringUtils.splitByLengthRepeated("", 2, 4, 1)  = [null, null, null]
>  *
>  * StringUtils.splitByLengthRepeated("abcdefghij", 2, 3)     = ["ab", "cde", "fg", "hij"]
>  * StringUtils.splitByLengthRepeated("abcdefgh", 2, 3)       = ["ab", "cde", "fg", "h"]
>  * StringUtils.splitByLengthRepeated("abcdefg", 2, 3)        = ["ab", "cde", "fg", null]
>  *
>  * StringUtils.splitByLengthRepeated(" abcdef", 2, 3)        = [" a", "bcd", "ef", null]
>  * StringUtils.splitByLengthRepeated("abcdef ", 2, 3)        = ["ab", "cde", "f ", null]
>  * StringUtils.splitByLengthRepeated("abcdef", 2, 3, 0, 1)   = ["ab", "cde", "", "f"]
>  * StringUtils.splitByLengthRepeated("abcdefg", 2, 3, 0, 1)  = ["ab", "cde", "", "f",
>  *                                                              "g", null, null, null]
>  * StringUtils.splitByLengthRepeated("abcdefgh", 2, 0, 1, 0) = ["ab", "", "c", "",
>  *                                                              "de", "", "f", "",
>  *                                                              "gh", "", null, null]
>  * StringUtils.splitByLengthRepeated("abcdefg", 2, 0, 1, 0) = ["ab", "", "c", "",
>  *                                                              "de", "", "f", "",
>  *                                                              "g", null, null, null]
>  * StringUtils.splitByLengthRepeated("abcdefg", -1)          = {@link IllegalArgumentException}
>  * StringUtils.splitByLengthRepeated("abcdefg", 0, 0)        = {@link IllegalArgumentException}
>  * </pre>
>  *
>  * @param str  the String to parse, may be null
>  * @param lengths  the string lengths where to cut, may be null, must not be negative
>  * @return an array of splitted Strings, {@code null} if null String input
>  * @throws IllegalArgumentException
>  *             if one of the lengths is negative or if lengths sum is less than 1
>  */
> public static String[] splitByLengthRepeatedly(String str, int... lengths);
> {code}
> See PR #75 : https://github.com/apache/commons-lang/pull/75



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