Write a mode method in Java to find the most frequently occurring element in an array

Question

The question goes:

Write a method called mode that returns the most frequently occurring element of an array of integers. Assume that the array has at le

Answer 1

Based on the answer from @codemania23 and the Java Docs for HashMap I wrote this code snipped and tests of a method that returns the most occurrent number in an array of numbers.

import java.util.HashMap;

public class Example {

    public int mostOcurrentNumber(int[] array) {
        HashMap map = new HashMap<>();
        int result = -1, max = 1;
        for (int arrayItem : array) {
            if (map.putIfAbsent(arrayItem, 1) != null) {
                int count = map.get(arrayItem) + 1;
                map.put(arrayItem, count);
                if (count > max) {
                    max = count;
                    result = arrayItem;
                }
            }
        }

        return result;
    }
}

Unit Tests

import org.junit.Test;

import static junit.framework.Assert.assertEquals;

public class ExampleTest extends Example {

    @Test
    public void returnMinusOneWhenInputArrayIsEmpty() throws Exception {
        int[] array = new int[0];
        assertEquals(mostOcurrentNumber(array), -1);
    }

    @Test
    public void returnMinusOneWhenElementsUnique() {
        int[] array = new int[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
        assertEquals(-1, mostOcurrentNumber(array));
    }

    @Test
    public void returnOne() throws Exception {
        int[] array = new int[]{0, 1, 0, 0, 1, 1, 1};
        assertEquals(1, mostOcurrentNumber(array));
    }

    @Test
    public void returnFirstMostOcurrentNumber() throws Exception {
        int[] array = new int[]{0, 1, 0, 1, 0, 0, 1, 1};
        assertEquals(0, mostOcurrentNumber(array));
    }
}