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 ?
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