Lists.partition() gives incorrect result when partition size is Integer.MAX_VALUE #616
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Original comment posted by boppenheim@google.com on 2011-05-04 at 07:00 AM The behavior is actually whenever you give a partition size >= Integer.MAX_VALUE - (list.size() - 2). On first thought, it seems odd to pass in values like Integer.MAX_VALUE. However, I guess you might be using MAX_VALUE to mean "give me a single partition". What is the use case where you want that though? I suppose we could special case when the partition size is >= to the size of the list. I'm not sure if its worth the extra logic or not. |
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Original comment posted by qforce.bak on 2011-05-04 at 08:11 AM I came across this oddity while I was working on an SWT-based table viewer that supports pagination. Internally, the table viewer uses Lists.partition() to split its input elements into pages of a fixed size. By default, the page size is set to Integer.MAX_VALUE so that the table viewer behaves like one without pagination support, i.e. by default it always displays a single page, just like an ordinary table viewer. |
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Original comment posted by finnw1 on 2011-05-04 at 09:12 AM @boppenheim, the special-casing you describe will not solve the problem for all cases. Consider: Here the partition size is smaller than the list, but the overflow still occurs. |
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Original comment posted by finnw1 on 2011-05-04 at 09:24 AM See this StackOverflow question for alternative ways to calculate the size that do not suffer from this bug: http://stackoverflow.com/questions/17944/how-to-round-up-the-result-of-integer-division This example is in C#, but everything here is also applicable to Java. |
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Original comment posted by kevinb@google.com on 2011-05-05 at 02:09 AM (No comment entered for this change.) Status: |
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Original comment posted by kevinb@google.com on 2011-07-13 at 06:18 PM (No comment entered for this change.) Status: |
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Original comment posted by kevinb@google.com on 2011-07-13 at 07:25 PM (No comment entered for this change.) Status: |
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Original comment posted by wasserman.louis on 2011-08-22 at 03:52 PM (No comment entered for this change.) Status: |
Original issue created by qforce.bak on 2011-05-02 at 07:06 PM
Hello,
It seems the method Lists.partition() behaves incorrectly when given a partition size of Integer.MAX_VALUE or Integer.MAX_VALUE - 1. The following snippet (based on Guava r08) demonstrates this:
List<String> list = Arrays.asList("a", "b", "c");
for (int i = 0; i < 5; i++) {
List<List<String>> partition = Lists.partition(list, Integer.MAX_VALUE - i);
System.out.println("size=" + partition.size() + " for i=" + i);
}
The console output is:
size=-1 for i=0
size=-1 for i=1
size=1 for i=2
size=1 for i=3
size=1 for i=4
I would expect size=1 if i=0 or i=1.
Best regards
Tran Nam Quang
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