Java Program to Initialize a List

In this article, we will understand how to initialize a list. A list is an ordered collection that allows us to store and access elements sequentially. It contains the index-based methods to insert, update, delete and search the elements. It can also have the duplicate elements.

Below is a demonstration of the same −

Suppose our input is −

Run the program

The desired output would be −

Initializing an integer list
The elements of the integer list are: [25, 60]

Initializing a string list
The elements of the string list are: [Java, Program]

Algorithm

Step 1 - START
Step 2 - Declare an integer list namely integer_list and a string list namely string_list
Step 3 - Define the values.
Step 4 - Use the List<Integer> integer_list = new ArrayList<Integer>() to initialize the integer list.
Step 5 - Use List<String> string_list = new ArrayList<String>() to initialize the integer list.
Step 6 - Use the function .add() to add items to the list.
Step 7 - Display the result
Step 8 - Stop

Example 1

Here, we bind all the operations together under the ‘main’ function.

import java.util.*;
public class Demo {
   public static void main(String args[]) {
      System.out.println("Required packages have been imported");
      System.out.println("\nInitializing an integer list");
      List<Integer> integer_list = new ArrayList<Integer>();
      integer_list.add(25);
      integer_list.add(60);
      System.out.println("The elements of the integer list are: " + integer_list.toString());
      System.out.println("\nInitializing a string list");
      List<String> string_list = new ArrayList<String>();
      string_list.add("Java");
      string_list.add("Program");
      System.out.println("The elements of the string list are: " + string_list.toString());
   }
}

Output

Required packages have been imported

Initializing an integer list
The elements of the integer list are: [25, 60]

Initializing a string list
The elements of the string list are: [Java, Program]

Example 2

Here, we encapsulate the operations into functions exhibiting object-oriented programming.

import java.util.*;
public class Demo {
   static void initialize_int_list(){
      List<Integer> integer_list = new ArrayList<Integer>();
      integer_list.add(25);
      integer_list.add(60);
      System.out.println("The elements of the integer list are: " + integer_list.toString());
   }
   static void initialize_string_list(){
      List<String> string_list = new ArrayList<String>();
      string_list.add("Java");
      string_list.add("Program");
      System.out.println("The elements of the string list are: " + string_list.toString());
   }
   public static void main(String args[]) {
      System.out.println("Required packages have been imported");
      System.out.println("\nInitializing an integer list");
      initialize_int_list();
      System.out.println("\nInitializing a string list");
      initialize_string_list();
   }
}

Output

Required packages have been imported

Initializing an integer list
The elements of the integer list are: [25, 60]

Initializing a string list
The elements of the string list are: [Java, Program]