Sort Collections in Java

Can someone please give an example and output of sorting an array in Java using a com开发者_StackOverflow中文版parator? I know I need to use public static void sort(List list, Comparator c);, but how does the comparator change the sorting order?

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Normally you can just implement Comparable and just pass the List to the sort() method. But if you need to use a Comparator instead here is a full example:

public static void main(String args[]) {
   List<ExampleItem> examples = new LinkedList<ExampleItem>();
   //Build List 
   Collections.sort(examples, new ExampleCompartor());//Sort with your comparator
}

//Custom Class to sort
class ExampleItem{
    private int data;
}

//Compartor
static class ExampleCompartor implements Comparator<ExampleItem>{
    @Override
    public int compare(ExampleItem ex1, ExampleItem ex2) {
        return ex1.data - ex2.data;
    }
}

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public class CompSample {
    public static int countVowels(String s) {
        return s.replaceAll("[^aeiouAEIOU]", "").length();
    }

    public static class NumberOfVowelsComparator implements Comparator<String> {
        public int compare(String o1, String o2) {
            int o1vowels = countVowels(o1);
            int o2vowels = countVowels(o2);

            return o2vowels - o1vowels;
        }
    }

    public static void main(String[] args) {
        String[] words = {"one", "two", "tree", "four"};
        List<String> sortedWords = Collections.sort(Arrays.asList(words),
            new NumberOfVowelsComparator());
        System.out.println(sortedWords);
    }
}

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Here is a good example of how to sort using comparator. http://www.javadeveloper.co.in/java-example/java-comparator-example.html