How do I sort list with comparator?

There are several ways to implement Comparators in Java:

Pass Comparator as argument to sort() method. Comparators, if passed to a sort method (such as Collections.
Implement Comparator in a separate class.
Pass Comparator to List.sort() method.

How do you sort collections in Java?

Example to sort Wrapper class objects

import java.util.*;
class TestSort3{
public static void main(String args[]){
ArrayList al=new ArrayList();
al.add(Integer.valueOf(201));
al.add(Integer.valueOf(101));
al.add(230);//internally will be converted into objects as Integer.valueOf(230)
Collections.sort(al);

How does comparator sort in Java?

Method 2: Using comparator interface- Comparator interface is used to order the objects of a user-defined class. This interface is present in java. util package and contains 2 methods compare(Object obj1, Object obj2) and equals(Object element). Using a comparator, we can sort the elements based on data members.

Which collection is best for sorting in Java?

If you want to maintain a sorted list which you will frequently modify (i.e. a structure which, in addition to being sorted, allows duplicates and whose elements can be efficiently referenced by index), then use an ArrayList but when you need to insert an element, always use Collections.

How do you sort an employee using comparator?

In order to sort Employee object on different criteria, we need to create multiple comparators e.g. NameComparator, AgeComparator, and SalaryComparator, this is known as custom sorting in Java. This is different from the natural ordering of objects, provided by the compareTo() method of java. lang.

How do you write a comparator in Java?

NameComparator.java

import java.util.*;
class NameComparator implements Comparator{
public int compare(Object o1,Object o2){
Student s1=(Student)o1;
Student s2=(Student)o2;
return s1.name.compareTo(s2.name);
}
}

How do I sort a collection list?

Code to sort the list in ascending order with Collections.sort() method:

public class ListSort_Java //Class for sorting the List in Java.
{
println(“The unsorted List is:”);
for (String myStr: myList) {
}
//Collections.sort() are used to sort the List.
println(“\nThe Sorted List is”);
for (String myStr: myList) {

Which sorting does Collections sort use?

So, in the end, Collections#sort uses Arrays#sort (of object elements) behind the scenes. This implementation uses merge sort or tim sort. According to the Javadoc, only primitive arrays are sorted using Quicksort. Object arrays are sorted with a Mergesort as well.

What are comparators in Java?

Java Comparator is an interface for sorting Java objects. comparator,” Java Comparator compares two Java objects in a “compare(Object 01, Object 02)” format. Using configurable methods, Java Comparator can compare objects to return an integer based on a positive, equal or negative comparison.

Does collections sort use CompareTo?

If any class implements Comparable interface in Java then collection of that object either List or Array can be sorted automatically by using Collections. sort() method and objects will be sorted based on there natural order defined by CompareTo method.

Which collection is faster in Java?

There is no fastest or best collection. If you need fast access to elements using index, ArrayList is your answer. If you need fast access to elements using a key, use HashMap . If you need fast add and removal of elements, use LinkedList (but it has a very poor index access performance).

Which collection we should prefer While sorting?

The best general purpose or ‘primary’ implementations are likely ArrayList , LinkedHashMap , and LinkedHashSet . Their overall performance is better, and you should use them unless you need a special feature provided by another implementation. That special feature is usually ordering or sorting.

How do I sort list with comparator?