Collections.sort() doesn't sort as it should

Question

I want to sort an Array of Strings with this Method:

private String[] sortAscending(String[] arrayToSort) {
    List<String> sortedList = Arrays.asList(arrayToSort);
    Collections.sort(sortedList);

    return (String[]) sortedList.toArray();
}

This will sort this Array

["Jens", "abCd", "test", "abC", "Peter"]

to this:

["Jens", "Peter", "abC", "abCd", "test"]

but it should be

["abC", "abCd", "Jens", "Peter", "test"]`

What am I doing wrong?

Upper case letters comes before lower case letters in ASCII table. — Rohit Jain, Aug 23 '14 at 15:03
Why convert array to list, sort it and convert it to another array? If you want to sort array instead of `Collections.sort` you can use `Arrays.sort`. — Pshemo, Aug 23 '14 at 15:25

Eran · Accepted Answer · 2014-08-23T15:19:28.083

6

The natural order of Strings in Java is lexicographical, which is case sensitive. Upper case letters will come before lower case letters.

Therefore you need to sort in case insensitive order :

Collections.sort(sortedList, String.CASE_INSENSITIVE_ORDER);

edited Aug 23 '14 at 15:19

answered Aug 23 '14 at 15:05

Eran

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@JaqenH'ghar-But,OP's question is all about English alphabets! – Am_I_Helpful Aug 23 '14 at 15:08
@JaqenH'ghar-It is though, but the questions are even smaller than being Locale-specific!!! – Am_I_Helpful Aug 23 '14 at 15:11
@Pshemo I assumed it was implied from my answer, by I can clarify. – Eran Aug 23 '14 at 15:16

score 2 · Answer 2 · answered Aug 23 '14 at 15:05

2

You should use a Collator, which orders strings using locale-sensitive rules. The default ordering of Strings is the pure lexicographic order (i.e. chars are ordered by their numeric Unicode value).

answered Aug 23 '14 at 15:05

JB Nizet

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Collections.sort() doesn't sort as it should

2 Answers2