Removing null Elements from a Java List – Techniques for Java 7, Java 8+, Apache Commons, Guava, and Groovy

The article explains how to remove null values from a List in different Java versions and with various libraries.

Java 7 or lower : Create a mutable list and call list.removeAll(Collections.singleton(null)); . Attempting the same on an immutable list throws java.lang.UnsupportedOperationException .

@Test
public void removeNull() {
    List
list = new ArrayList<>(Arrays.asList("A", null, "B", null));
    list.removeAll(Collections.singleton(null));
    assertThat(list, hasSize(2));
}

Java 8 or higher – using removeIf :

@Test
public void removeNull() {
    List
list = new ArrayList<>(Arrays.asList("A", null, "B", null));
    list.removeIf(Objects::isNull);
    assertThat(list, hasSize(2));
}

If you prefer to keep the original list unchanged, you can create a new list with streams:

@Test
public void removeNull() {
    List
list = new ArrayList<>(Arrays.asList("A", null, "B", null));
    List
newList = list.stream().filter(Objects::nonNull).collect(Collectors.toList());
    assertThat(list, hasSize(4));
    assertThat(newList, hasSize(2));
}

Apache Commons Collections provides CollectionUtils.filter with a non‑null predicate:

@Test
public void removeNull() {
    List
list = new ArrayList<>(Arrays.asList("A", null, "B", null));
    CollectionUtils.filter(list, PredicateUtils.notNullPredicate());
    assertThat(list, hasSize(2));
}

Google Guava offers two approaches:

@Test
public void removeNull() {
    List
list = new ArrayList<>(Arrays.asList("A", null, "B", null));
    Iterables.removeIf(list, Predicates.isNull());
    assertThat(list, hasSize(2));
}

Or, to obtain a new list without modifying the original:

@Test
public void removeNull() {
    List
list = new ArrayList<>(Arrays.asList("A", null, "B", null));
    List
newList = new ArrayList<>(Iterables.filter(list, Predicates.notNull()));
    assertThat(list, hasSize(4));
    assertThat(newList, hasSize(2));
}

Groovy solution using a closure:

List
list = new ArrayList<>(Arrays.asList("A", null, "B", null));

def re = list.findAll { it != null }

assert re == ["A", "B"]

The article concludes with a disclaimer that the content is original and should not be republished without permission, followed by a curated list of other technical articles.