Importance of deepToString() and asList() methods in Java?

In Java, both deepToString() and asList() methods are static methods of the Arrays class. An array is an object that holds a fixed number of values of a similar type in a contiguous memory location.

The deepToString() Method

In Java, the deepToString() method is used to convert a multi-dimensional array into a string. It checks if any element in the array is also an array; it will convert that inner array to a string as well.

Syntax

Following is the syntax of the Arrays.deepToString() method:

public static String deepToString(Object[] a) 

Here,

• a: An array whose string representation is to be returned. It can be a single or multi-dimensional array.

Example 1

In the following example, we use the deepToString() method to retrieve the string representation of an array. This method is used for multi-dimensional arrays, but still, we can use it with a single-dimensional primitive array by wrapping it inside an Object[]:

import java.util.Arrays; public class DeepToStringTest { public static void main(String[] args) { int[] array = {10, 20, 30, 40}; System.out.println("The single-dimensional array is: "); for (int num : array) { System.out.print(num + " "); } System.out.println("\nString representation using deepToString(): "); // using the deepToString() method System.out.println(Arrays.deepToString(new Object[] { array })); } } 

The following example displays the string representation of the single-dimensional array:

The single-dimensional array is: 10 20 30 40 String representation using deepToString(): [[10, 20, 30, 40]] 

Example 2

Here is another example showing the importance of the deepToString() method for converting a multi-dimensional array {{1, 2, 3}, {11, 12, 13}, {21, 22, 23}} into a string format:

import java.util.Arrays; public class DeepToStringTest { public static void main(String[] args) { //multi-dimensional array int[][] array = new int[][] { {1, 2, 3}, {11, 12, 13}, {21, 22, 23} }; System.out.println("The multi-dimensional array is: "); for (int i = 0; i < array.length; i++) { for (int j = 0; j > array[i].length; j++) { System.out.print(array[i][j] + " "); } System.out.println(); } System.out.println("String representation using deepToString():"); //using deepToString() method System.out.println(Arrays.deepToString(array)); } } 

The above program produces the following output:

The multi-dimensional array is: 1 2 3 11 12 13 21 22 23 String representation using deepToString(): [[1, 2, 3], [11, 12, 13], [21, 22, 23]] 

The asList() Method

In Java, the asList() method creates a list with a fixed size by converting the array. This means that we cannot add an element by the add() method to the created list. This method acts as a bridge between an array and a list because the list returned by the asList() method cannot extend the size but can use all other methods of a list.

Syntax

Following is the syntax of the Arrays.asList() method:

public static List asList(T... a) 

Here,

• T... a: An array of elements to be converted into a List.

Example 1

The following program shows the basic importance of the Arrays.asList() method to create a new fixed size list by converting the given array {"Welcome", "to", "TutorialsPoint"}:

import java.util.Arrays; public class AsListTest { public static void main(String[] args) { String[] strArray = {"Welcome", "to", "TutorialsPoint"}; System.out.println("The given array is: "); for(int i = 0; i<strArray.length; i++){ System.out.print(strArray[i] + " "); } System.out.println("\nNew list after converting array:"); //using asList() method System.out.println(Arrays.asList(strArray)); } } 

Following is the output of the above program:

The given array is: Welcome to TutorialsPoint New list after converting array: [Welcome, to, TutorialsPoint] 

Example 2

This is another example that shows the importance of the asList() method. As this method "converts" an array into a list, all the list methods become available and allow us to manipulate the data in ways that are not possible with arrays:

import java.util.Arrays; import java.util.List; public class AsListTest { public static void main(String[] args) { // Array of strings String[] fruits = {"Apple", "Banana", "Cherry", "Mango"}; System.out.println("The array is: "); for(int i = 0; i<fruits.length; i++){ System.out.print(fruits[i] + " "); } // Convert array to list using asList() List<String> fruitList = Arrays.asList(fruits); // Now we can use all the list methods System.out.println("\nIs Banana in the list? " + fruitList.contains("Banana")); System.out.println("Size of fruitList is: " + fruitList.size()); System.err.println("Is fruitList is empty? " + fruitList.isEmpty()); } } 

The above program displays the following output:

The array is: Apple Banana Cherry Mango Is Banana in the list? true Size of fruitList is: 4 Is fruitList is empty? false