How To Sort ArrayList In Java – Collections.Sort() Examples

How To Sort ArrayList In Java :

In this post, we will learn how to sort ArrayList in java. This is very easy to understand and remember the methods.

1) Sorting ArrayList in ascending order
2) Sorting ArrayList in descending order

ArrayList in Java

Sorting List in Ascending order:

package com.java.w3schools;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

public class FruitsArrayList {

      public static void main(String[] args) {

            List<String> fruits = new ArrayList<>();

            fruits.add("Mango");

            fruits.add("Orange");

            fruits.add("Apple");

            fruits.add("Banana");

            System.out.println("Printing fruits before sorting : " + fruits);

            Collections.sort(fruits);

            System.out.println("Printing fruits after sorting : " + fruits);

      }

}

Output:

Printing fruits before sorting : [Mango, Orange, Apple, Banana]

Printing fruits after sorting : [Apple, Banana, Mango, Orange]

Collections class has a method sort() which takes List as argument. This method does sorting in ascending order. Observer the output of the above program.

Sorting List in Descending order:

Just replace the Collection.sort with the following code snippet.

Collections.sort(fruits, Collections.reverseOrder());

Output:

Printing fruits before sorting : [Mango, Orange, Apple, Banana]

Printing fruits after sorting : [Orange, Mango, Banana, Apple]

Collections class has a method for sorting the list elements in reverse order that is descending order.

In the next post, we will learn how to sort a list of students where Student is a user defined class with properties of id, name, age.

Java ArrayList remove Example: How to remove by index, by Value/Object, for a specific range

How to remove a value from ArrayList in java with example programs.

In this post, we will learn how to program to remove elements from a ArrayList in java. Removing value can be done in three ways.

1) By index
2) By value or Object
3) For a given specific range

ArrayList api provides various methods to do remove operations.

Encapsulation in Java with Examples

What is Encapsulation in Java 

Encapsulation is one of the principle of OOPs.

Encapsulation describes the ability of hiding data and methods of object.
Encapsulation is a process of arranging information about data and behavior into a single component like as object in Java.

Keeping all members and methods are within bounds of class. In Java, all class are under encapsulated.

If we set all fields of class as private, so no other code outside of this class can not access private variables. To access these private variables, we have to declare public methods in class.


So these private members are not accessible by outside objects or classes.

A class can have authority to modify the values using setter and getter methods of class. By using getter methods, we can make read-only and wise versa for write-only.

3 Ways to Find Sum of First n numbers program in Java

In this post, You will learn today today how to find sum of first n numbers in java using while loop, for loop and mathematics formula(Optimized).

For this program, we have to input the natural number n value which you want to get the sum. So that Our program will get sum of first n numbers. This is basic program for freshers or who are studying engineering in their lab programs.

Example 1:
number = 10
sum = 55

Example 2:
number = 100
sum = 5050