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https://issues.apache.org/jira/browse/LANG-1124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14546732#comment-14546732
]
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_r30460736
--- 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"]
--- End diff --
Like said in the next line : `StringUtils.splitByLength("abcdefg", 2, 2)`
will return `["ab", "cd" ]`.
`StringUtils.splitByLength("abcdefghij", 2, 4, 1) = ["ab", "cdef", "g"]`
I asked myself the question during development. Do we discard the extra
characters ?
I think it would be nice to let users decide. Moreover, depending on use
case, it could be useful to keep/discard the "first extra characters" (like
parsing a single line commented out string).
I propose to :
* add a private `splitByLengthWorker(String string, boolean splitFromEnd,
boolean discardExtraChar, int ... lengths)`
* keep this `splitByLength(String, int ...)` method logic as default :
`return splitByLengthWorker(string, false, true, lengths)`. So, by default, the
returned array is same size as the `int ... lengths` array param and this
behavior is interesting on parsing "fixed column lengths" strings.
* add a `splitByLengthKeepExtraChar(String, int ...)` : `return
splitByLengthWorker(string, false, false, lengths)`
* add a `splitByLengthFromEnd(String, int ...)` : `return
splitByLengthWorker(string, true, false, lengths)`
* add a `splitByLengthFromEndKeepExtraChar(String, int ...)` : `return
splitByLengthWorker(string, true, true, lengths)`
A question : For _split from end_ methods, which call do you think is more
logic : _right aligned/end to start_ lengths, _reversed/not reversed_ result ?
* `StringUtils.splitByLengthFromEndKeepExtraChar("__abcdef", 1, 2, 3) =
["__", "a", "bc", "def"]` - (RA, NR)
* `StringUtils.splitByLengthFromEndKeepExtraChar("__abcdef", 1, 2, 3) =
["def", "bc", "a", "__"]` - (RA, R)
* `StringUtils.splitByLengthFromEndKeepExtraChar("__abcdef", 1, 2, 3) =
["f", "de", "abc", "__"]` - (E2S, R)
* `StringUtils.splitByLengthFromEndKeepExtraChar("__abcdef", 1, 2, 3) =
["__", "abc", "de", "f"]` - (E2S, NR)
I think the first one is more readable, we can visually understand the
splitting, but may be less intuitive :
```
StringUtils.splitByLengthFromEnd("ABCDEFGHIJKLM", 3, 4, 5) = ["BCD",
"EFGH", "IJKLM"]
[3][4_][_5_]
ABCDEFGHIJKLM
```
> 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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