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ArrayList allows duplicate values while HashSet doesn't allow duplicates values. Ordering : ArrayList maintains the order of the object in which they are inserted while HashSet is an unordered collection and doesn't maintain any order.
List. sort() does not remove duplicates.
A simple solution would be to use efficient sorting algorithms like Merge Sort, Quicksort, Heapsort, etc., that can solve this problem in O(n. log(n)) time, but those will not take advantage of the fact that there are many duplicated values in the array. A better approach is to use a counting sort.
One of the most common ways to find duplicates is by using the brute force method, which compares each element of the array to every other element. This solution has the time complexity of O(n^2) and only exists for academic purposes.
Use a Comparator like this:
List<Fruit> fruits= new ArrayList<Fruit>();
Fruit fruit;
for(int i = 0; i < 100; i++)
{
fruit = new Fruit();
fruit.setname(...);
fruits.add(fruit);
}
// Sorting
Collections.sort(fruits, new Comparator<Fruit>() {
@Override
public int compare(Fruit fruit2, Fruit fruit1)
{
return fruit1.fruitName.compareTo(fruit2.fruitName);
}
});
Now your fruits list is sorted based on fruitName.
Implement Comparable interface to Fruit.
public class Fruit implements Comparable<Fruit> {
It implements the method
@Override
public int compareTo(Fruit fruit) {
//write code here for compare name
}
Then do call sort method
Collections.sort(fruitList);
Try BeanComparator from Apache Commons.
import org.apache.commons.beanutils.BeanComparator;
BeanComparator fieldComparator = new BeanComparator("fruitName");
Collections.sort(fruits, fieldComparator);
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