Convert a String to a List of Characters in Java

Given a String, the task is to convert it into a List of Characters in Java.

Examples:

Input: String = "Geeks"
Output: [G, e, e, k, s]

Input: String = "GeeksForGeeks"
Output: [G, e, e, k, s, F, o, r, G, e, e, k, s]

Below are the various ways to do so:

1. Naive Method

   Approach:

   1. Get the String.
   2. Create an empty List of Characters.
   3. Add each character of String to the List.
   4. Return the List.

   Below is the implementation of the above approach:

   
   

   
   
   

   // Java program to illustrate // Converting a String to a List // of Characters import java.util.*;    // Java program to convert // a String to a List of Characters    class GFG {        // Function to convert String     // to List of Characters     public static List<Character>     convertStringToCharList(String str)     {            // Create an empty List of character         List<Character> chars = new ArrayList<>();            // For each character in the String         // add it to the List         for (char ch : str.toCharArray()) {                chars.add(ch);         }            // return the List         return chars;     }        // Driver code     public static void main(String[] args)     {            // Get the String to be converted         String str = "Geek";            // Get the List of Character         List<Character>             chars = convertStringToCharList(str);            // Print the list of characters         System.out.println(chars);     } }

   Output:

   [G, e, e, k]
   

2. Using Java 8 Stream:

   Approach:

   1. Get the String.
   2. Create a List of Characters.
   3. Convert to String to IntStream using chars() method.
   4. Convert IntStream to Stream using mapToObj() method.
   5. Collect the elements as a List Of Characters using collect()
   6. Return the List.

   Below is the implementation of the above approach:

   
   

   
   
   

   // Java program to illustrate // Converting a String to a List // of Characters import java.util.*; import java.util.stream.Collectors;    // Java program to convert // a String to a List of Characters    class GFG {        // Function to convert String     // to List of Characters     public static List<Character>     convertStringToCharList(String str)     {          // Create an empty List of character       List<Character> chars = str          // Convert to String to IntStream       .chars()          // Convert IntStream to Stream<Character>       .mapToObj(e -> (char)e)          // Collect the elements as a List Of Characters       .collect(Collectors.toList());          // return the List       return chars;     }        // Driver code     public static void main(String[] args)     {            // Get the String to be converted         String str = "Geek";            // Get the List of Character         List<Character>             chars = convertStringToCharList(str);            // Print the list of characters         System.out.println(chars);     } }

   Output:

   [G, e, e, k]
   

3. Using Java 8 Stream:

   Approach:

   1. Get the String.
   2. Use the AbstractList interface to convert the String into List of Character
   3. Return the List.

   Below is the implementation of the above approach:

   
   

   
   
   

   import java.util.*;    // Java program to convert // a String to a List of Characters    class GFG {        // Function to convert String     // to List of Characters     public static List<Character>     convertStringToCharList(String str)     {         return new AbstractList<Character>() {                @Override             public Character get(int index)             {                 return str.charAt(index);             }                @Override             public int size()             {                 return str.length();             }         };     }        // Driver code     public static void main(String[] args)     {            // Get the String to be converted         String str = "Geek";            // Get the List of Character         List<Character>             chars = convertStringToCharList(str);            // Print the list of characters         System.out.println(chars);     } }

   Output:

   [G, e, e, k]
   

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