minor java testing work

core-java/src/test/java/org/baeldung/java/collections/JavaCollectionCleanupUnitTest.java

@@ -0,0 +1,53 @@
+package org.baeldung.java.collections;
+
+import static org.hamcrest.Matchers.hasSize;
+import static org.junit.Assert.assertThat;
+
+import java.util.List;
+
+import org.apache.commons.collections4.CollectionUtils;
+import org.apache.commons.collections4.PredicateUtils;
+import org.junit.Test;
+
+import com.google.common.base.Predicates;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+
+public class JavaCollectionCleanupUnitTest {
+
+    // removing nulls
+
+    @Test
+    public final void givenListContainsNulls_whenRemovingNullsWithPlainJava_thenCorrect() {
+        final List<Integer> list = Lists.newArrayList(null, 1, null);
+        while (list.remove(null))
+            ;
+
+        assertThat(list, hasSize(1));
+    }
+
+    @Test
+    public final void givenListContainsNulls_whenRemovingNullsWithGuavaV1_thenCorrect() {
+        final List<Integer> listWithNulls = Lists.newArrayList(null, 1, null);
+        Iterables.removeIf(listWithNulls, Predicates.isNull());
+
+        assertThat(listWithNulls, hasSize(1));
+    }
+
+    @Test
+    public final void givenListContainsNulls_whenRemovingNullsWithGuavaV2_thenCorrect() {
+        final List<Integer> listWithNulls = Lists.newArrayList(null, 1, null, 2, 3);
+        final List<Integer> listWithoutNulls = Lists.newArrayList(Iterables.filter(listWithNulls, Predicates.notNull()));
+
+        assertThat(listWithoutNulls, hasSize(3));
+    }
+
+    @Test
+    public final void givenListContainsNulls_whenRemovingNullsWithCommonsCollections_thenCorrect() {
+        final List<Integer> list = Lists.newArrayList(null, 1, 2, null, 3, null);
+        CollectionUtils.filter(list, PredicateUtils.notNullPredicate());
+
+        assertThat(list, hasSize(3));
+    }
+
+}