[COLLECTIONS-586] PatriciaTrie prefixMap clear throws NullPointerException

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.1
• Assignee: Unassigned
• Reporter: Shailender Bathula
• Created: 12/Apr/16 21:59
• Updated: 18/Jul/17 18:56
• Resolved: 04/Aug/16 17:33

Description

Clearing all entries of a prefixMap returned by PatriciaTrie using the clear method throws a NullPointerException. The workaround of removing each entry using the remove method seems to work.

Here are the test cases for the bug and the workaround:

public class PatriciaTrieTest {

    private Trie<String, Integer> trie;

    @Before
    public void setUp() {
        trie = new PatriciaTrie<Integer>();
        trie.put("Anna", 1);
        trie.put("Anael", 2);
        trie.put("Analu", 3);
        trie.put("Andreas", 4);
        trie.put("Andrea", 5);
        trie.put("Andres", 6);
        trie.put("Anatole", 7);
    }

    @Test
    public void testPrefixMapClear() {
        SortedMap<String, Integer> prefixMap = trie.prefixMap("And");
        assertEquals(new HashSet<>(Arrays.asList("Andrea", "Andreas", "Andres")), prefixMap.keySet());
        assertEquals(Arrays.asList(5, 4, 6), new ArrayList<>(prefixMap.values()));

        prefixMap.clear();
        assertTrue(prefixMap.keySet().isEmpty());
        assertTrue(prefixMap.values().isEmpty());
        assertEquals(new HashSet<>(Arrays.asList("Anael", "Analu", "Anatole", "Anna")), trie.keySet());
        assertEquals(Arrays.asList(2, 3, 7, 1), new ArrayList<>(trie.values()));
    }

    @Test
    public void testPrefixMapClearUsingRemove() {
        SortedMap<String, Integer> prefixMap = trie.prefixMap("And");
        assertEquals(new HashSet<>(Arrays.asList("Andrea", "Andreas", "Andres")), prefixMap.keySet());
        assertEquals(Arrays.asList(5, 4, 6), new ArrayList<>(prefixMap.values()));

        Set<String> keys = new HashSet<String>(prefixMap.keySet());
        for (final String key : keys) {
            prefixMap.remove(key);
        }
        assertTrue(prefixMap.keySet().isEmpty());
        assertTrue(prefixMap.values().isEmpty());
        assertEquals(new HashSet<>(Arrays.asList("Anael", "Analu", "Anatole", "Anna")), trie.keySet());
        assertEquals(Arrays.asList(2, 3, 7, 1), new ArrayList<>(trie.values()));
    }

}

The stacktrace of the NullPointerException thrown by the testPrefixMapClear test case is:

java.lang.NullPointerException
	at org.apache.commons.collections4.trie.AbstractPatriciaTrie$PrefixRangeEntrySet$EntryIterator.remove(AbstractPatriciaTrie.java:2370)
	at java.util.AbstractCollection.clear(AbstractCollection.java:432)
	at java.util.AbstractMap.clear(AbstractMap.java:288)
	at PatriciaTrieTest.testPrefixMapClear(PatriciaTrieTest.java:39)

Issue Links

• links to: GitHub Pull Request #18