How to Create a Generic List in Java?

Java is a potent programming language that can be used to create a vast array of desktop, online, and mobile apps. The List interface is one of Java's core data structures. A list is a group of elements that are arranged in a certain order and may include duplicates. We will look at how to create a generic List in Java in this tutorial.

What is a Generic List in Java?

A generic List in Java is a grouping of elements of a particular kind. ArrayList, LinkedList, and Vector are just a few of the classes that implement the general List interface, which is specified in the java.util package. Developers can create a collection of components of any type and benefit from type safety at compile time by using a generic List.

Creating a Generic List in Java

To create a generic List in Java, we need to follow these steps:

Step 1: Import the required packages

In Java, we need to import the java.util package to use the List interface.

Step 2: Declare the List

The List must then be declared using the general syntax. Within angle brackets (>), we describe the kind of elements we want to store in the List.

To create a list of numbers, for instance, we might declare it as follows:

This declares a List named integerList that can store elements of type Integer. We have used the ArrayList class to implement the List interface.

Step 3: Add elements to the List

After declaring the List, we can add elements to it using the add() method.

For example, to add an integer to the integerList, we would use the following code:

It adds the integer value 10 to the end of the List.

Step 4: Access elements of the List

We can access the elements of the List using the get() method.

For example, to get the first element of the integerList, we would use the following code:

This retrieves the first element of the List and stores it in the variable firstElement.

Step 5: Iterate over the List

We can iterate over the elements of the List using a for loop.

For example, to print all the elements of the integerList, we would use the following code:

for (int i = 0; i < integerList.size(); i++) {
System.out.println(integerList.get(i));
}

It iteratively prints each element of the List to the console.

Any Java developer must possess the fundamental ability to create a generic List in Java. You can create a List of any type and carry out activities like adding and accessing entries as well as iterating over the List by following the instructions provided in this article. Generic Lists offer type safety and enable more robust and maintainable programming.

TheJava programme builds a generic List of strings, elements are added to it, and the result is printed to the console. The user is prompted to enter each string when the programme asks for their input on how many strings to add to the list.

GenericListExample.java

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class GenericListExample {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("How many strings do you want to add to the list? ");
        int numStrings = scanner.nextInt();
        List<String> stringList = new ArrayList<String>();
        for (int i = 0; i < numStrings; i++) {
            System.out.print("Enter string " + (i+1) + ": ");
            String inputString = scanner.next();
            stringList.add(inputString);
        }
        System.out.println("The strings in the list are:");
        for (String str : stringList) {
            System.out.println(str);
        }
    }
}

Output:

How many strings do you want to add to the list? 3
Enter string 1: apple
Enter string 2: banana
Enter string 3: orange
The strings in the list are:
apple
banana
orange

In this example, the user inputs 3 as the number of strings to add to the list. The user is then prompted by the programme to enter each string individually. The programme prints each string in the list to the console when all strings have been added to the list.

Advantages of Using Generic Lists

Using generic Lists in Java has several advantages:

Type safety: By specifying the type of elements that the List can contain; we can avoid runtime errors caused by adding elements of the wrong type.

Reusability: Generic Lists can be used with any type of element, making them a flexible and reusable data structure.

Performance: Many List implementations, such as ArrayList, offer fast access and modification times.

Familiarity: Lists are a commonly used data structure in computer science, making them a familiar and intuitive choice for many developers.

Next TopicJava Extend Multiple Classes

← prev next →