Arrays.asList() in Java

Arrays.asList() is a useful method in Java, which is part of the java.util.Arrays class. This method is used to return a fixed-size list backed by the specified array. In this way, it acts as a bridge between array-based and collection-based APIs, along with Collection.toArray(). The returned list is serializable and implements RandomAccess, making it a useful tool for data manipulation.

The syntax of the asList() method is straightforward. It takes an array a, which is required to be converted into a List, as a parameter, and returns a list view of the specified array.

Let's look at some examples of how this method works in Java:

Example 1: Working of asList() method in Java

java
import java.util.*; 

public class Example1 { 
    public static void main(String[] args) 
    { 
        String arr[] = { "GfG", "IDE", "Courses"}; 

        List<String> list = Arrays.asList(arr); 

        System.out.println(list); 
    }
} 

Output:
[GfG, IDE, Courses]

Example 2: Internal working of asList() method in Java

java
import java.util.*; 

public class Example2 { 
    public static void main(String[] args) 
    { 
        String arr[] = {"GfG", "IDE", "Courses"}; 

        List<String> list = Arrays.asList(arr); 
        
        arr[0] = "Practice";

        System.out.println(list); 
        
        list.set(1, "Premium");
        
        System.out.println(Arrays.toString(arr));
    }
} 

Output:
[Practice, IDE, Courses]
[Practice, Premium, Courses]

One important thing to note is that the list returned by the asList() method is a fixed size, and nothing can be added or removed from the list in Java.

However, there are several practical applications of the asList() method in Java, such as reversing a list or creating a collection from the array elements. Let's take a look at some examples:

Reversing a list

java
import java.util.*; 

public class Example3 { 
    public static void main(String[] args) 
    { 
        String arr[] = {"GfG", "IDE", "Courses"};
        
        Collections.reverse(Arrays.asList(arr));
        
        System.out.println(Arrays.toString(arr));
    }
} 

Output:
[Courses, IDE, GfG]

Creating a Collection from the array elements

java
import java.util.*; 

public class Example4 { 
    public static void main(String[] args) 
    { 
        String arr[] = {"GfG", "IDE", "Courses"};
        
        HashSet<String> s 
        = new HashSet<String>(
            Arrays.asList(arr));
        
        System.out.println(s);
    }
} 

Output:
[GfG, Courses, IDE]

In conclusion, the asList() method in Java is an efficient way of converting an array into a fixed-size list. It has many practical applications, such as reversing a list or creating a collection from the array elements. By understanding how this method works and how to use it, you can save yourself time and effort in your Java programming.