Does Java have an alphabetical order like this?

user_17677104 0
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Like in this example, https://www.duden.de/rechtschreibung/Regen_Niederschlag , the words are sorted in the following way: "regelwidrig, Regelwidrigkeit, Regelzeit, regen, Regen, Regenabflussrohr, Regenanlage, regenarm, Regenbö, Regenbogen..." that is, it is a "more non-case-sensitive" sorting than Collections.Sort() automatically does. Lowercase words come before uppercase ones like "regen, Regen".

ArrayList<String> regen = new ArrayList<String>( );
for(String x : new String[]{"regelwidrig", "Regelwidrigkeit", "Regelzeit",
        "regen", "Regen", "Regenabflussrohr",
        "Regenanlage", "regenarm", "Regenbö", "Regenbogen"}) {
        regen.add(x);
}

Collections.sort(regen) response:

[Regelwidrigkeit, Regelzeit, Regen, Regenabflussrohr, Regenanlage, Regenbogen, Regenbö,
regelwidrig, regen, regenarm]// lowercase at the end

I can implement a comparator for this, but I'd rather take one-liner of code to get this way of sorting. Such as: Collections.SomeMethod(regen); or Collections.Sort(regen, some_extra_parameter); But I haven't found after deep google search, unfortunately.

alphabetical-sort arraylist sorting java
4 Answers

Collators

Use the Collator class for locale-sensitive String comparison.

Specifically, Java has support for German collators:

Collator collator = Collator.getInstance(Locale.GERMAN);
regen.sort(collator);

Example:

List<String> inputs = new ArrayList <>(
    List.of( "regelwidrig", "Java", "Regelwidrigkeit", "Regelzeit", "regen", "Regen", "Regenabflussrohr", "Regenanlage", "regenarm", "Regenbö", "Regenbogen" )
);
inputs.sort( java.text.Collator.getInstance( Locale.GERMAN ) ) ;

[Java, regelwidrig, Regelwidrigkeit, Regelzeit, regen, Regen, Regenabflussrohr, Regenanlage, regenarm, Regenbö, Regenbogen]

user_49455350

  • You can use String.CASE_INSENSITIVE_ORDER to order strings in case-insensitive way.

  • If you also at the same time want to farther specify order of elements which current comparator considers as equal (like String.CASE_INSENSITIVE_ORDER would do for "Regen" and "regen") then you can use Comparator#thenComparing method and pass to it Comparator which would sort those equal elements like you want.

    • Assuming you would also want to order "Regen", "regen" as "regen", "Regen" (lower-case before upper-case) you can simply reverse their natural order with Comparator.reverseOrder().

So your code can look like:

regen.sort(String.CASE_INSENSITIVE_ORDER.thenComparing(Comparator.reverseOrder()));

Demo:

ArrayList<String> regen = new ArrayList<String>(
        Arrays.asList("regelwidrig", "Regelwidrigkeit", "Regelzeit",
            "Regen", "regen", "Regenabflussrohr",
            "Regenanlage", "regenarm", "Regenbö", "Regenbogen")
);

regen.sort(String.CASE_INSENSITIVE_ORDER.thenComparing(Comparator.reverseOrder()));
System.out.println(regen);

Result: [regelwidrig, Regelwidrigkeit, Regelzeit, regen, Regen, Regenabflussrohr, Regenanlage, regenarm, Regenbogen, Regenbö]

(notice "Regen", "regen" ware swapped)

user_13937660

Just use a oneliner "Comparator.comparing"

List<String> regen = new ArrayList<String>( );
for(String x : new String[]{"regelwidrig", "Regelwidrigkeit", "Regelzeit",
        "regen", "Regen", "Regenabflussrohr",
        "Regenanlage", "regenarm", "Regenbö", "Regenbogen"}) {
        regen.add(x);
}

Collections.sort(regen, Comparator.comparing(s -> s.toLowerCase()));
System.out.println(regen);

Result will be:

regelwidrig, Regelwidrigkeit, Regelzeit, regen, Regen, Regenabflussrohr, Regenanlage, regenarm, Regenbogen, Regenbö

user_4605570

The reason why strings are sorted the way they are naturally sorted is because the ASCII values for these characters have a lower value for UPPERCASE than for lowercase. In this case, all words starts with "R" and the ASCII value of uppercase "R" is 82 (52 hex), whereas lowercase "R" is 114 (72 hex). For that reason, Regen will precede regen when sorting in natural order (in Java).

So, using plain Java

public static void main(String[] args) {
    List<String> words = Arrays.asList(new String[]{"regelwidrig", "Regelwidrigkeit", "Regelzeit", "regen", "Regen", "Regenabflussrohr", "Regenanlage", "regenarm", "Regenbö", "Regenbogen"});
    Collections.sort(words);
    System.out.println(words);
}

Will output

[Regelwidrigkeit, Regelzeit, Regen, Regenabflussrohr, Regenanlage, Regenbogen, Regenbö, regelwidrig, regen, regenarm]

As you can see, all words starts with "R", but sorting puts all capitalized words ahead of ones that start with lowercase.

As @Pshemo indicated in his answer, you can (should) code your comparator account for case sensitivity and to reverse the order of lowercase vs uppercase as needed.

user_28513110
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