GWT, ListHandler> columnSortHandler does not sort properly

Question

I got these code:

           ListHandler<List<String>> columnSortHandler = new ListHandler<List<String>>(
                    list);
            columnSortHandler.setComparator(nameColumn,
                    new Comparator<List<String>>() {
                      public int compare(List<String> o1, List<String> o2) {
                        if (o1 == o2) {
                          return 0;
                        }

                        // Compare the name columns.
                        if (o1 != null) {
                          return (o2 != null) ? o1.get(0).compareTo(o2.get(0)) : 1;
                        }
                        return -1;
                      }
                    });

                table.addColumnSortHandler(columnSortHandler);

When sorting column contains iPhone 1, iPhone 2, iPhone 3... then it sorts correctly ie, iPhone 1, iPhone 2, iPhone 3 for ascending & iPhone 3, iPhone 2, iPhone 1 for decending

But when sorting column contains:

1.92 MP
3.15 MP AF 0.31 MP
3.2 MP
5 MP AF and flash
1.3 MP
1.3 MP
2 MP (rear); 0.3 MP (front)
1.92 MP AF with flash (rear)

it follows no correct order, it didn't even put the 2 "1.3 MP" cell next to each other. The correct order for the above list should be:
1.3 MP
1.3 MP
1.92 MP
1.92 MP AF with flash (rear)
2 MP (rear); 0.3 MP (front)
3.15 MP AF 0.31 MP
3.2 MP
5 MP AF and flash

Is there anything wrong with the code above?

score 0 · Answer 1 · answered Apr 11 '13 at 15:31

0

As the author of website said the java sorting algorithm is based on ASCII.It never works as a human thinks. :) rude but fact.

People sort strings with numbers differently than software does.

Use The Alphanum Algorithm

In the above link download AlphanumComparator.java and use it.

answered Apr 11 '13 at 15:31

Suresh Atta

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@Baadshah How does the sorting of numbers explain Tom's issue with not putting the "1.3 MP" cells next to each other? I agree that "1", "2", and "10" will sort in the order "1, 10, 2" using an ASCII sort, but this doesn't explain Tom's problem. – Andy King Apr 11 '13 at 17:09
@Tom I think your problem is that you're using the "==" operator when comparing `String` values ... you need to use `String#compareTo` (in fact, I'm not sure why you're writing your own comparator, since the `String#compareTo` will suffice). – Andy King Apr 11 '13 at 17:12
@andy are you sure that compareTo will give what tom is asking even with numbers in string..? – Suresh Atta Apr 11 '13 at 17:45
@Baadshah `String#compareTo` should work with the example strings that Tom has identified. It won't work for "1", "2", and "10" however. – Andy King Apr 11 '13 at 22:11

score 0 · Answer 2 · edited Feb 08 '18 at 09:59

I also add o1.get(0).compareTo(o2.get(0))==0 into the code as what Any King suggested, but the sorting is still very messy.

ListHandler<List<String>> columnSortHandler = new ListHandler<List<String>>(
                list);
        columnSortHandler.setComparator(nameColumn,
                new Comparator<List<String>>() {
                  public int compare(List<String> o1, List<String> o2) {
                    if (o1.get(0).compareTo(o2.get(0))==0) {
                      return 0;
                    }

                    // Compare the name columns.
                    if (o1 != null) {
                      return (o2 != null) ? o1.get(0).compareTo(o2.get(0)) : 1;
                    }
                    return -1;
                  }
                });

            table.addColumnSortHandler(columnSortHandler);

score 0 · Answer 3 · answered Apr 11 '13 at 17:54

I think the problem is

ListHandler<List<String>>

& not the java sorting algorithm cos look at Gwt Sample http://gwt.googleusercontent.com/samples/Showcase/Showcase.html#!CwCellTable, it sort the address beautifully & the code use very simple compare. look at sample gwt code for sorting address

 addressColumn.setSortable(true);
addressColumn.setDefaultSortAscending(false);
sortHandler.setComparator(addressColumn, new Comparator<ContactInfo>() {
  @Override
  public int compare(ContactInfo o1, ContactInfo o2) {
    return o1.getAddress().compareTo(o2.getAddress());
  }
});

GWT, ListHandler> columnSortHandler does not sort properly

3 Answers3