JUnit Assert.assertNotNull() Method Example

assertNotNull() method belongs to JUnit 4 org.junit.Assert class. In JUnit 5 all JUnit 4 assertion methods are moved to org.junit.jupiter.api.Assertions class.

When to use assertNotNull() method or assertion

When we want to assert that an object is not null we can use the assertNotNull assertion.

void org.junit.Assert.assertNotNull(Object object)

Asserts that an object isn't null. If it is an AssertionError is thrown. 
  • object - Object to check or null

Assert.assertNotNull(Object object) Method Example

When we want to assert that an object is not null we can use the assertNotNull assertion:
import static org.junit.Assert.assertNotNull;

import java.util.Arrays;
import java.util.Collection;

import org.junit.Test;

import com.javaguides.strings.StringUtility;

public class AssertNotNullExample {
    public static String[] toStringArray(final Collection<?> collection) {
        if (collection == null) {
             return null;
       return collection.toArray(new String[collection.size()]);

 public void toStringArrayTest() {
      final String[] strArray = StringUtility.toStringArray(Arrays.asList("a", "b", "c"));
      for (final String element : strArray) {


Related JUnit Examples

  1. JUnit Assert.assertArrayEquals() Method Example
  2. JUnit Assert.assertEquals() Method Example
  3. JUnit Assert.assertTrue() Method Example
  4. JUnit Assert.assertFalse() Method Example
  5. JUnit Assert.assertNull() Method Example
  6. JUnit Assert.assertNotNull() Method Example
  7. JUnit Assert.assertSame() Method Example
  8. JUnit Assert.assertNotSame() Method Example
  9. JUnit Assert.fail() Method Example