Convert an ArrayList of String to a String array in Java

Given an ArrayList of String, the task is to convert the ArrayList to String array in java.

Examples:

Input: ArrayList = [ "Geeks", "for", "Geeks" ]
Output: String[] = {"Geeks", "for", "Geeks"}

Input: ArrayList = [ "Jupiter", "Saturn", "Uranus", "Neptune", "Sun"]
Output: String[] = {"Jupiter", "Saturn", "Uranus", "Neptune", "Sun"}

1. Using ArrayList.get() Method

   Syntax:

   
   
   
   

    str[j] = a1.get(j)

   Approach:

   1. Get the ArrayList of Strings.
   2. Find the size of ArrayList using size() method, and Create a String Array of this size.
   3. Fetch each element of the ArrayList one by one using get() method.
   4. Assigned each element into String Array using assignment(=) operator.
   5. Print String Array.

   Below is the implementation of the above approach:

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   // Java program to Convert ArrayList to // String ArrayList using get() method    import java.util.*;    public class GFG {        // Function to convert ArrayList<String> to String[]     public static String[] GetStringArray(ArrayList<String> arr)     {            // declaration and initialise String Array         String str[] = new String[arr.size()];            // ArrayList to Array Conversion         for (int j = 0; j < arr.size(); j++) {                // Assign each value to String array             str[j] = arr.get(j);         }            return str;     }        // Driver code     public static void main(String[] args)     {            // declaration and initialise ArrayList         ArrayList<String>             a1 = new ArrayList<String>();            a1.add("Geeks");         a1.add("for");         a1.add("Geeks");            // print ArrayList         System.out.println("ArrayList: " + a1);            // Get String Array         String[] str = GetStringArray(a1);            // Print Array elements         System.out.print("String Array[]: "                          + Arrays.toString(str));     } }

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   Output:

   ArrayList: [Geeks, for, Geeks]
   String Array[]: [Geeks, for, Geeks]
   

2. Using Object array as intermediate

   Syntax:

   Object[] arr = a1.toArray()
   String str = (String)obj;
   

   Approach:

   1. Get the ArrayList of String.
   2. Convert ArrayList to Object array using toArray() method.
   3. Iterate and convert each element to desired type using typecasting. Here it is converted to String type and added to the String Array.
   4. Print String Array.

   Below is the implementation of the above approach:

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   // Java program to Convert ArrayList to // String ArrayList using get() method    import java.util.*;    public class GFG {        // Function to convert ArrayList<String> to String[]     public static String[] GetStringArray(ArrayList<String> arr)     {            // declaration and initialise String Array         String str[] = new String[arr.size()];            // Convert ArrayList to object array         Object[] objArr = arr.toArray();            // Iterating and converting to String         int i = 0;         for (Object obj : objArr) {             str[i++] = (String)obj;         }            return str;     }        // Driver code     public static void main(String[] args)     {            // declaration and initialise ArrayList         ArrayList<String>             a1 = new ArrayList<String>();            a1.add("Geeks");         a1.add("for");         a1.add("Geeks");            // print ArrayList         System.out.println("ArrayList: " + a1);            // Get String Array         String[] str = GetStringArray(a1);            // Print Array elements         System.out.print("String Array[]: "                          + Arrays.toString(str));     } }

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   Output:

   ArrayList: [Geeks, for, Geeks]
   String Array[]: [Geeks, for, Geeks]
   

3. Using copyOf() method:

   Syntax:

   Object[] gfg= a1.toArray()
   String[] str = Arrays.copyOf(gfg, 
                                gfg.length, 
                                String[].class);
   

   Approach:

   1. Get the ArrayList of String.
   2. Convert ArrayList to Object array using toArray() method.
   3. Convert it to String Array using Arrays.copyOf() method.
   4. Print String Array.

   Below is the implementation of the above approach:

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   // Java program to Convert ArrayList to // String ArrayList using get() method    import java.util.*;    public class GFG {        // Function to convert ArrayList<String> to String[]     public static String[] GetStringArray(ArrayList<String> arr)     {            // Convert ArrayList to object array         Object[] objArr = arr.toArray();            // convert Object array to String array         String[] str = Arrays                            .copyOf(objArr, objArr                                                .length,                                    String[].class);            return str;     }        // Driver code     public static void main(String[] args)     {            // declaration and initialise ArrayList         ArrayList<String>             a1 = new ArrayList<String>();            a1.add("Geeks");         a1.add("for");         a1.add("Geeks");            // print ArrayList         System.out.println("ArrayList: " + a1);            // Get String Array         String[] str = GetStringArray(a1);            // Print Array elements         System.out.print("String Array[]: "                          + Arrays.toString(str));     } }

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   Output:

   ArrayList: [Geeks, for, Geeks]
   String Array[]: [Geeks, for, Geeks]
   

Rajput-Ji

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