DoubleArrayTrie里的LongestSearcher的next方法需要进行强化，当传入的treemap的value为null时…

src/main/java/com/hankcs/hanlp/collection/trie/DoubleArrayTrie.java

@@ -1299,7 +1299,7 @@ public LongestSearcher(int offset, char[] charArray)
          */
         public boolean next()
         {
-            value = null;
+            length = 0;
             begin = i;
             int b = base[0];
             int n;
@@ -1309,15 +1309,15 @@ public boolean next()
             {
                 if (i >= arrayLength)               // 指针到头了，将起点往前挪一个，重新开始，状态归零
                 {
-                    return value != null;
+                    return length > 0;
                 }
                 p = b + (int) (charArray[i]) + 1;   // 状态转移 p = base[char[i-1]] + char[i] + 1
                 if (b == check[p])                  // base[char[i-1]] == check[base[char[i-1]] + char[i] + 1]
                     b = base[p];                    // 转移成功
                 else
                 {
                     if (begin == arrayLength) break;
-                    if (value != null)
+                    if (length > 0)
                     {
                         i = begin + length;         // 输出最长词后，从该词语的下一个位置恢复扫描
                         return true;

src/test/java/com/hankcs/hanlp/collection/trie/DoubleArrayTrieTest.java

@@ -54,6 +54,37 @@ public void testLongestSearcher() throws Exception
         }
     }
 
+    public void testLongestSearcherWithNullValue() {
+        TreeMap<String, String> buildFrom = new TreeMap<String, String>();
+        TreeMap<String, String> buildFromValueNull = new TreeMap<String, String>();
+        String[] keys = new String[]{"he", "her", "his"};
+        for (String key : keys) {
+            buildFrom.put(key, key);
+            buildFromValueNull.put(key, null);
+        }
+        DoubleArrayTrie<String> trie = new DoubleArrayTrie<String>(buildFrom);
+        DoubleArrayTrie<String> trieValueNull = new DoubleArrayTrie<String>(buildFromValueNull);
+
+        String text = "her3he6his-hers! ";
+
+        DoubleArrayTrie<String>.LongestSearcher searcher = trie.getLongestSearcher(text.toCharArray(), 0);
+        DoubleArrayTrie<String>.LongestSearcher searcherValueNull = trieValueNull.getLongestSearcher(text.toCharArray(), 0);
+
+        while (true) {
+            boolean next = searcher.next();
+            boolean nextValueNull = searcherValueNull.next();
+
+            if (next && nextValueNull) {
+                assertTrue(searcher.begin == searcherValueNull.begin && searcher.length == searcherValueNull.length);
+            } else if (next || nextValueNull) {
+                assert false;
+                break;
+            } else {
+                break;
+            }
+        }
+    }
+
     public void testTransmit() throws Exception
     {
         DoubleArrayTrie<CoreDictionary.Attribute> dat = CustomDictionary.DEFAULT.dat;