#vulnerable code 
                                @Test
    public void testClear() {
        Assert.assertEquals(100, trie.get("杨尚川"), 0);
        Assert.assertEquals(1, trie.get("中华人民共和国"), 0);
        trie.clear();
        Assert.assertEquals(null, trie.get("杨尚川"));
        Assert.assertEquals(null, trie.get("中华人民共和国"));
    } 
                            #location 3 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testClear() {
        assertEquals(100, genericTrie.get("杨尚川").intValue());
        assertEquals(1, genericTrie.get("中华人民共和国").intValue());
        genericTrie.clear();
        assertEquals(null, genericTrie.get("杨尚川"));
        assertEquals(null, genericTrie.get("中华人民共和国"));
    }