Sort ArrayList based on a on object property

Question

I have a ArrayList<CustomObject> myFinalList = new ArrayList<CustomObject>(); The list has a ojbect property "NumberOfLikes" for each entry in the list. "NumberOfLikes" are String values.

I have derived these values into an array like so:-

ArrayList<String> numberOfLikes = new ArrayList<String>();

        for(int j =0; j<myFinalList.size(); j++)
        {
            String likes = myFinalList.get(j).getNewsLikes();
            numberOfLikes.add(likes);
        }


        numberofLikesArray=  numberOfLikes.toArray(new String[numberOfLikes.size()]);

    int[] numberofLikesArrayInt = new int[numberofLikesArray.length];

    for (int n = 0; n < numberofLikesArray.length; n++) 
    {
        numberofLikesArrayInt[n] = Integer.parseInt(numberofLikesArray[n]);
    }
    Arrays.sort(numberofLikesArrayInt);
    ArrayList<Integer> intAarrylistlikes = new ArrayList<Integer>();
    for (int i = 0; i < numberofLikesArrayInt.length; i++) 
    {
        intAarrylistlikes.add(numberofLikesArrayInt[i]);
    }
    Collections.reverse(intAarrylistlikes);
    numberofLikesArrayInt = convertIntegers(intAarrylistlikes);
    numberofLikesArray = Arrays.toString(numberofLikesArrayInt).split("[\\[\\]]")[1].split(", ");

    for (int i = 0; i < numberofLikesArray.length; i++) 
    {
        companyNewsList = Lists.newArrayList(Collections2.filter(myFinalList, new ArticleFilter2(numberofLikesArray[i])));
    }

ArticleFilter2.java

public class ArticleFilter2 implements Predicate<News>
{
    private final Pattern pattern;

    public ArticleFilter2(final String regex)
    {
        pattern = Pattern.compile(regex);
    }

    @Override
    public boolean apply(final CustomObject input)
    {
        return pattern.matcher(input.getLikes()).find();
    }
}

Now this array consists of the "NumberOfLikes" in descending order. Now I want to create another ArrayList which sorts the "MyFinalList" according to these values ie:- item having the maximum likes should appear first.

How can I do it?

Is it possible to add a property (getter and setter) for the numberOfLikes to the CumstomObject class? — Bob Brinks
– Bob Brinks, Commented May 5, 2014 at 8:46

JimVanB · Accepted Answer · 2014-05-05 08:54:39Z

2

This asks for a Comparator with your Custom Class. http://docs.oracle.com/javase/7/docs/api/java/util/Comparator.html

Make a new class that implements Comparator and implement this method:

public class YourComparator<CustomClass> implements Comparator{
    @Override
    public int compare ( CustomClass obj1, CustomClass obj2 ) {
        return (int) (obj1.getYourProperty() - obj2.getYourProperty());
    }
}

Use it:

Collections.sort(MyFinalList, new YourComparator());

edited May 5, 2014 at 8:54

answered May 5, 2014 at 8:49

JimVanB

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2 Comments

user3534519 Over a year ago

The property i want to sort the List is a String

JimVanB Over a year ago

It doesn't matter what type this list is. In the compare method you can implement your own compare logic on those string values.

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