Program to convert Array to Set in Java

An array is a group of like-typed variables that are referred to by a common name. An array can contain primitives data types as well as objects of a class depending on the definition of the array. In case of primitives data types, the actual values are stored in contiguous memory locations. In case of objects of a class, the actual objects are stored in heap segment.

Set in Java is a part of java.util package and extends java.util.Collection interface. It does not allow the use of duplicate elements and at max can accommodate only one null element. Few important features of Java Set interface are as follows:

  • The set interface is an unordered collection of objects in which duplicate values cannot be stored.
  • The Java Set does not provide control over the position of insertion or deletion of elements.
  • Basically, Set is implemented by HashSet, LinkedHashSet or TreeSet (sorted representation).
  • Set has various methods to add, remove clear, size, etc to enhance the usage of this interface.

Examples:

Input: Array: [Geeks, forGeeks, A computer Portal]
Output: Set: [Geeks, forGeeks, A computer Portal]

Input: Array: [1, 2, 3, 4, 5]
Output: Set: [1, 2, 3, 4, 5]



Below are methods to convert Array to Set in Java:

  1. Brute Force or Naive Method: In this method, an empty Set is created and all elements present of the Array are added to it one by one.

    Algorithm:

    1. Get the Array to be converted.
    2. Create an empty Set
    3. Iterate through the items in the Array.
    4. For each item, add it to the Set
    5. Return the formed Set

    Program:

    filter_none

    edit
    close

    play_arrow

    link
    brightness_4
    code

    // Java Program to convert
    // Array to Set
      
    import java.util.*;
    import java.util.stream.*;
      
    class GFG {
      
        // Generic function to convert an Array to Set
        public static <T> Set<T> convertArrayToSet(T array[])
        {
      
            // Create an empty Set
            Set<T> set = new HashSet<>();
      
            // Iterate through the array
            for (T t : array) {
                // Add each element into the set
                set.add(t);
            }
      
            // Return the converted Set
            return set;
        }
      
        public static void main(String args[])
        {
            // Create an Array
            String array[] = { "Geeks", "forGeeks"
                                         "A Computer Portal" };
      
            // Print the Array
            System.out.println("Array: " + Arrays.toString(array));
      
            // convert the Array to Set
            Set<String>
                set = convertArrayToSet(array);
      
            // Print the Set
            System.out.println("Set: " + set);
        }
    }

    chevron_right

    
    

    Output:

    Array: [Geeks, forGeeks, A computer Portal]
    Set: [Geeks, forGeeks, A computer Portal]
    
  2. Using Arrays.asArray() method: In this method, the Array is passed as the parameter into the Set constructor in the form of an Array with the help of Arrays.asArray() method.

    Algorithm:

    1. Get the Array to be converted.
    2. Create the Set by passing the Array as parameter in the constructor of the Set with the help of Arrays.asArray() method
    3. Return the formed Set

    Program:

    filter_none

    edit
    close

    play_arrow

    link
    brightness_4
    code

    // Java Program to convert
    // Array to Set
      
    import java.util.*;
    import java.util.stream.*;
      
    class GFG {
      
        // Generic function to convert an Array to Set
        public static <T> Set<T> convertArrayToSet(T array[])
        {
      
            // Create the Set by passing the Array
            // as parameter in the constructor
            Set<T> set = new HashSet<>(Arrays.asList(array));
      
            // Return the converted Set
            return set;
        }
      
        public static void main(String args[])
        {
            // Create an Array
            String array[] = { "Geeks", "forGeeks",
                                        "A computer Portal" };
      
            // Print the Array
            System.out.println("Array: " + Arrays.toString(array));
      
            // convert the Array to Set
            Set<String>
                set = convertArrayToSet(array);
      
            // Print the Set
            System.out.println("Set: " + set);
        }
    }

    chevron_right

    
    

    Output:

    Array: [Geeks, forGeeks, A computer Portal]
    Set: [Geeks, forGeeks, A computer Portal]
    
  3. Using Collections.addAll(): Since Set is a part of the Collection package in Java. Therefore the Array can be converted into the Set with the help of Collections.addAll() method.

    Algorithm:

    1. Get the Array to be converted.
    2. Create an empty Set.
    3. Add the array into the Set by passing it as the parameter to the Collections.addAll() method.
    4. Return the formed Set

    Program:

    filter_none

    edit
    close

    play_arrow

    link
    brightness_4
    code

    // Java Program to convert
    // Array to Set
      
    import java.util.*;
    import java.util.stream.*;
      
    class GFG {
      
        // Generic function to convert an Array to Set
        public static <T> Set<T> convertArrayToSet(T array[])
        {
      
            // Create the Set by passing the Array
            // as parameter in the constructor
            Set<T> set = new HashSet<>();
      
            // Add the array to set
            Collections.addAll(set, Arrays.toString(array));
      
            // Return the converted Set
            return set;
        }
      
        public static void main(String args[])
        {
            // Create an Array
            String array[] = { "Geeks", "forGeeks",
                                        "A computer Portal" };
      
            // Print the Array
            System.out.println("Array: " + array);
      
            // convert the Array to Set
            Set<String>
                set = convertArrayToSet(array);
      
            // Print the Set
            System.out.println("Set: " + set);
        }
    }

    chevron_right

    
    

    Output:



    Array: [Geeks, forGeeks, A computer Portal]
    Set: [Geeks, forGeeks, A computer Portal]
    
  4. Using Java 8 Stream API: HashSet constructor can take another collection object to construct a new set containing the elements of the specied array.

    Algorithm:

    1. Get the Array to be converted.
    2. Convert the array to Stream
    3. Convert the Stream to Set using Collectors.toSet()
    4. Collect the formed set using collect() method
    5. Return the formed Set

    Program:

    filter_none

    edit
    close

    play_arrow

    link
    brightness_4
    code

    // Java Program to convert
    // Array to Set in Java 8
      
    import java.util.*;
    import java.util.stream.*;
      
    class GFG {
      
        // Generic function to convert array to set
        public static <T> Set<T> convertArrayToSet(T array[])
        {
            // create a set from the Array
            return Arrays
                .stream(array)
                .collect(Collectors.toSet());
        }
      
        public static void main(String args[])
        {
            // Create an Array
            String array[] = { "Geeks", "forGeeks"
                                        "A computer Portal" };
      
            // Print the Array
            System.out.println("Array: " + Arrays.toString(array));
      
            // convert the Array to Set
            Set<String>
                set = convertArrayToSet(array);
      
            // Print the Set
            System.out.println("Set: " + set);
        }
    }

    chevron_right

    
    

    Output:

    Array: [Geeks, forGeeks, A computer Portal]
    Set: [Geeks, forGeeks, A computer Portal]
    
  5. Using Guava Sets.newHashSet(): Sets.newHashSet() creates a mutable HashSet instance containing the elements of the specified array.

    Algorithm:

    1. Get the Array to be converted.
    2. Create an empty Set.
    3. Add the array into the Set by passing it as the parameter to the Sets.newHashSet() method.
    4. Return the formed Set
    filter_none

    edit
    close

    play_arrow

    link
    brightness_4
    code

    // Java Program to convert
    // Array to Set in Java 8
      
    import static com.google.common.collect.Sets.*;
    import java.util.*;
    import java.util.stream.*;
      
    class GFG {
      
        // Generic function to convert array to set
        public static <T> Set<T> convertArrayToSet(T array[])
        {
            // create a set from the Array
            return Sets.newHashSet(array);
        }
      
        public static void main(String args[])
        {
            // Create an Array
            String array[] = { "Geeks", "forGeeks"
                                        "A computer Portal" };
      
            // Print the Array
            System.out.println("Array: " + Arrays.toString(array));
      
            // convert the Array to Set
            Set<String>
                set = convertArrayToSet(array);
      
            // Print the Set
            System.out.println("Set: " + set);
        }
    }

    chevron_right

    
    

    Output:

    Array: [Geeks, forGeeks, A computer Portal]
    Set: [Geeks, forGeeks, A computer Portal]
    


My Personal Notes arrow_drop_up

Technical Content Engineer at GeeksForGeeks

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.