Sorting an ArrayList of objects using a custom sorting order

user_218027 0
Viewed 184983

I am looking to implement a sort feature for my address book application.

I want to sort an ArrayList<Contact> contactArray. Contact is a class which contains four fields: name, home number, mobile number and address. I want to sort on name.

How can I write a custom sort function to do this?

arraylist collections sorting java
12 Answers

Ok, I know this was answered a long time ago... but, here's some new info:

Say the Contact class in question already has a defined natural ordering via implementing Comparable, but you want to override that ordering, say by name. Here's the modern way to do it:

List<Contact> contacts = ...;

contacts.sort(Comparator.comparing(Contact::getName).reversed().thenComparing(Comparator.naturalOrder());

This way it will sort by name first (in reverse order), and then for name collisions it will fall back to the 'natural' ordering implemented by the Contact class itself.

user_51034580

use this method:

private ArrayList<myClass> sortList(ArrayList<myClass> list) {
    if (list != null && list.size() > 1) {
        Collections.sort(list, new Comparator<myClass>() {
            public int compare(myClass o1, myClass o2) {
                if (o1.getsortnumber() == o2.getsortnumber()) return 0;
                return o1.getsortnumber() < o2.getsortnumber() ? 1 : -1;
            }
        });
    }
    return list;
}

`

and use: mySortedlist = sortList(myList); No need to implement comparator in your class. If you want inverse order swap 1 and -1

user_106259440

With java 8 feature

List<Contact> contact = contactArray.stream().sorted((c1, c2) -> ((c1.getName().compareTo(c2.getName())))).collect(Collectors.toList());
user_113232400
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