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Java Forum / General / June 2005Bug in String's split method???
I was trying to write a utility method that work almost the same as the split method on String, that would work with java versions 1.3 or less, using Jakarta's ORO library. I though I implemented it according to the javadoc for the split method on String. But the expression "".split(",", 0), returns an array with 1 element, I was expecting an array with no elements. The expression ",".split(",", 0) returns an array with no elements. Is this a bug or am I reading the docs wrong? Code: String[] result = null; result = "".split(",", 0); System.out.println(result.length); result = ",".split(",", 0); System.out.println(result.length); System.out.println(System.getProperty("java.version")); Output: 1 0 1.4.2_06 I thing the output should be: 0 0 1.4.2_06 > I was trying to write a utility method that work almost the same as the > split method on String, that would work with java versions 1.3 or less, [quoted text clipped - 24 lines] > 0 > 1.4.2_06 Why? the regex expression is not found in your string, so it cant be split, you called the split() method on a string, so if no splitting occurs there's always one part left; the original string. > I was trying to write a utility method that work almost the same as > the split method on String, that would work with java versions 1.3 or [quoted text clipped - 25 lines] > 0 > 1.4.2_06 From java doc for String.split (asterisks/bold added for emphasis): The array returned by this method contains each substring of this string that is terminated by another substring that matches the given expression or is terminated by the end of the string. The substrings in the array are in the order in which they occur in this string. *If the expression does not match any part of the input then the resulting array has just one element, namely this string.*  SignatureVirgil Yes I saw that part, but the part that throws me is the limit parameter. Here are the docs on that. Not the asterisks. The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. If the limit n is greater than zero then the pattern will be applied at most n - 1 times, the array's length will be no greater than n, and the array's last entry will contain all input beyond the last matched delimiter. If n is non-positive then the pattern will be applied as many times as possible and the array can have any length. *If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded.* ------ I think that the poriton you emphasized "f the expression does not match any part of the input then the resulting array has just one element, namely this string." and the portion I emphasized "If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded." conflict with eachother in the case "".split(",", 0); The limit was zero so the empty trailing field should have been discarded. I could read the docs both ways. The docs are ambiguous on this feature. > Yes I saw that part, but the part that throws me is the limit > parameter. Here are the docs on that. Not the asterisks. [quoted text clipped - 25 lines] > discarded. I could read the docs both ways. The docs are ambiguous > on this feature. I see no conflict or ambiguity. As you pointed out, *trailing* empty strings will be discarded. There is no trailing empty string until there is a delimiter. The beginning of the string is not a delimiter with respect to the pattern, IMHO. The section I quoted above is the rule to be used in a special case... when there are no pattern matches. The second section you quoted is only in force when there is at least one pattern match. I assume it was intended to prevent the return of an empty string element when the pattern matched the tail characters of the string. SignatureVirgil > > Yes I saw that part, but the part that throws me is the limit > > parameter. Here are the docs on that. Not the asterisks. [quoted text clipped - 35 lines] > prevent the return of an empty string element when the pattern matched the > tail characters of the string. I see nothing in the docs that mention the removal of trailing empty strings, is only in force when there is at least 1 pattern match. >>> Yes I saw that part, but the part that throws me is the limit >>> parameter. Here are the docs on that. Not the asterisks. [quoted text clipped - 41 lines] >> -- >> Virgil I submit that the definition of "trailing" implies that there is something to "trail" and that the "something" must be at least one pattern match. The documentation indicating that empty strings are removed is *only* predicated upon those empty strings be *trailing* empty strings. What does you example empty string trail behind? Anyway, you may choose to use any definition of "trailing" that justifies your conclusion that there is a bug or that the documentation is ambiguous. I will continue to use the one that indicates there is something (a matched token) to be trailing behind, the one that fits the documented (as I read it) and actual behavior of the class. 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