This example demonstrates you how to remove duplicate elements from an array using the help of java.util.HashSet class.

package org.kodejava.util;

import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class ArrayRemoveDuplicate {
    public static void main(String[] args) {
        // A string array with duplicate values.
        String[] data = {"A", "C", "B", "D", "A", "B", "E", "D", "B", "C"};
        System.out.println("Original array         : " + Arrays.toString(data));

        // Convert a string array into java.util.List because we need a list
        // object to create the java.util.Set object.
        List<String> list = Arrays.asList(data);

        // A set is a collection object that cannot have a duplicate values,
        // by converting the array to a set the duplicate value will be removed.
        Set<String> set = new HashSet<>(list);

        // Convert the java.util.Set back to array using the toArray() method of
        // the set object copy the value in the set to the defined array.
        String[] result = set.toArray(new String[0]);
        System.out.println("Array with no duplicate: " + Arrays.toString(result));
    }
}

The result of the code snippet above:

Original array         : [A, C, B, D, A, B, E, D, B, C]
Array with no duplicate: [A, B, C, D, E]

package org.kodejava.util;

import java.util.*;

public class ArrayToSetExample {
    public static void main(String[] args) {
        Integer[] numbers = {7, 7, 8, 9, 10, 8, 8, 9, 6, 5, 4};

        // To convert an array into a java.util.Set firstly we need to convert the
        // array into a java.util.List using the Arrays.asList() method. With the
        // List object created we can instantiate a new java.util.HashSet and pass
        // the list as the constructor parameter.
        List<Integer> numberList = Arrays.asList(numbers);
        Set<Integer> numberSet = new HashSet<>(numberList);

        // Or we can simply combine the line above into single line.
        Set<Integer> anotherNumberSet = new HashSet<>(Arrays.asList(numbers));

        // Display what we get in the set using iterator.
        for (Iterator<Integer> iterator = numberSet.iterator(); iterator.hasNext(); ) {
            Integer number = iterator.next();
            System.out.print(number + ", ");
        }

        // Display what we get in the set using for-each.
        for (Integer number : anotherNumberSet) {
            System.out.print(number + ", ");
        }
    }
}