Java Program to Convert Array to Set (HashSet) and Vice-Versa
Example 1: Convert Array to Set
import java.util.*;public class ArraySet {public static void main(String[] args) {String[] array = {"a", "b", "c"};Set<String> set = new HashSet<>(Arrays.asList(array));System.out.println("Set: " + set);}}
When you run the program, the output will be:
Set: [a, b, c]
In the above program, we’ve an array named array. To convert array to set, we first convert it to a list using asList() as HashSet accepts list as a constructor.
Then, we initialize set with the elements of the converted list.
Example 2: Convert Array to Set using stream
import java.util.*;public class ArraySet {public static void main(String[] args) {String[] array = {"a", "b", "c"};Set<String> set = new HashSet<>(Arrays.stream(array).collect(Collectors.toSet()));System.out.println("Set: " + set);}}
The output of the program is same as Example 1.
In the above program, instead of converting array to list and then to a set, we use stream to convert to set.
We first convert the array to stream using stream() method and use collect() method with toSet() as parameter to convert the stream to a set.
Example 3: Convert Set to Array
import java.util.*;public class SetArray {public static void main(String[] args) {Set<String> set = new HashSet<>();set.add("a");set.add("b");set.add("c");String[] array = new String[set.size()];set.toArray(array);System.out.println("Array: " + Arrays.toString(array));}}
When you run the program, the output will be:
Array: [a, b, c]
In the above program, we’ve a HashSet named set. To convert set into an array, we first create an array of length equal to the size of the set and use toArray() method.