Convert ArrayList to String and Vice Versa in Java

In this article, we will understand how to convert the ArrayList into a string and vice versa. The ArrayList class is a resizable array, which can be found in the java. util package. The difference between a built-in array and an ArrayList in Java is that the size of an array cannot be modified.

ArrayList definition

• It supports all optional list operations and allows null elements.
  
• It provides methods to adjust the size of the underlying array used to store the list.
  
• Its constant factor is lower than that of the LinkedList implementation.

Convert an ArrayList to a string

To convert an ArrayList to a string using the to String method. It creates an ArrayList, adds elements, and then converts it to a string. The following are the steps to convert an ArrayList to a string ?

• Step 1: Initialize the ArrayList: We create an ArrayList and add some string elements to it using the add method.
  

ArrayList input_array = new ArrayList<>();
input_array.add("Java");
input_array.add("Python");
input_array.add("Scala");
input_array.add("JavaScript");

• Step 2: Convert the ArrayList to a String: The toString method is used to convert the ArrayList into a string representation.
  

String result_string = input_array.toString();

Example 1

 The following is an example of converting an ArrayList to a string ?

import java.util.ArrayList;
public class Demo {
	public static void main(String[] args) {
		System.out.println("The required packages have been imported");
		ArrayList input_array= new ArrayList<>();
		input_array.add("Java");
		input_array.add("Python");
		input_array.add("Scala");
		input_array.add("JavaScript");
		System.out.println("The array is defined as: " + input_array);
		String result_string = input_array.toString();
		System.out.println("\nThe result string is: " + result_string);
	}
}

Output

The required packages have been imported
The array is defined as: [Java, Python, Scala, JavaScript]

The result string is: [Java, Python, Scala, JavaScript]

Convert a string to an array

To convert a string into a character array we define a string, initialize an array of the same length, and then iterate over the string to store each character in the array. The following are the steps to convert a string to an array ?

• Step 1: Define the String: We start by defining a string variable that we want to convert into an array.

String input_string = "Java Program";
System.out.println("The string is defined as: " + input_string);

• Step 2: Initialize the Array: We create a character array of the same length as the input string to hold the characters.
  

char[] result_array = new char[input_string.length()];

• Step 3: Convert String to Array: We use a loop to iterate over the string and store each character in the array.
  

for (int i = 0; i < input_string.length(); i++) {
   result_array[i] = input_string.charAt(i);
}

Example 2

The following is an example of converting a string to an array. ?

public class Demo {
	public static void main(String args[]) {
		String input_string = "Java Program";
		System.out.println("The string is defined as: " + input_string);
		char[] result_array = new char[input_string.length()];
		for (int i = 0; i < input_string.length(); i++) {
			result_array[i] = input_string.charAt(i);
		}
		System.out.println("The array after conversion from string is: " );
		for (char c : result_array) {
			System.out.print(c + " ");
		}
	}
}

Output

The string is defined as: Java Program
The array after conversion from string is:
J a v a  P r o g r a m