How to sort an Arraylist in java

Before java 8 (when there was no functional programming in java), there were traditional ways of sorting arraylist in java using Comparable and Comparator interfaces.

For details visit the below links about Comparable and Comparator.

Sorting ArrayList With Comparable

Sorting Arraylist in java using Comparator

Sorting ArrayList using Comparator

Sorting Arraylist with lambda expressions

Functional programming which was introduced in java 8 has made it very easy to sort arraylist using forEach method and lambda expression. Observe the below example

Collections.sort(cList, (c1, c2) -> c1.getName().compareTo(c2.getName()));

You can see that it can be done in just one line. In this example, c1, c2 represent Cricketer class objects and sorting is done on a property called name which is String data type. Refer the full example below.

Sorting arraylist in java using lambda

Cricketer.java

package com.jts;

public class Cricketer {

	private String name;
	private int noOfRuns;

	//getter and setters
	//constructors
	//toString

}

ArraylistSortingExample.java

package com.jts;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class ArraylistSortingExample {
	
	public static void main(String[] args) {
		
		List<Cricketer> cList = new ArrayList<>();
		cList.add(new Cricketer("Virat Kohli", 10000));
		cList.add(new Cricketer("Rohit Sharma", 8000));
		cList.add(new Cricketer("Steven Smith", 8500));
		cList.add(new Cricketer("Kane Williamson", 7000));
		
		System.out.println("Before sorting : " + cList);
		//sorting using lambda
		Collections.sort(cList, (c1, c2) -> c1.getName().compareTo(c2.getName()));
		
		System.out.println("After sorting on name : " + cList);
		
	}
}

To know more about java8 features, follow the below link

Java 8 Features