Question

I would like to create an HashMap where the key is a string and the value is a List. All the values are taken from a Mysql table. The problem is that I have an HashMap where the key is the right one while the value is not the right one, because it is overwritten. In fact I have for all different keys the same list with the same content.
This is the code:

public static HashMap<String,List<Table_token>> getHashMapFromTokenTable() throws SQLException, Exception{

DbAccess.initConnection();
List<Table_token> listFrom_token = new ArrayList();
HashMap<String,List<Table_token>> hMapIdPath = new HashMap<String,List<Table_token>>();

String query = "select * from token";
resultSet = getResultSetByQuery(query);

while(resultSet.next()){

    String token=resultSet.getString(3);
    String path=resultSet.getString(4);
    String word=resultSet.getString(5);
    String lemma=resultSet.getString(6);
    String postag=resultSet.getString(7);
    String isTerminal=resultSet.getString(8);
    Table_token t_token = new Table_token();
    t_token.setIdToken(token);
    t_token.setIdPath(path);
    t_token.setWord(word);
    t_token.setLemma(lemma);
    t_token.setPosTag(postag);
    t_token.setIsTerminal(isTerminal);
    listFrom_token.add(t_token);
    System.out.println("path "+path+" path2: "+token);
    int row = resultSet.getRow();

    if(resultSet.next()){
        if((resultSet.getString(4).compareTo(path)!=0)){    
            hMapIdPath.put(path, listFrom_token);
                listFrom_token.clear();
            }
        resultSet.absolute(row);

    }
    if(resultSet.isLast()){
        hMapIdPath.put(path, listFrom_token);
            listFrom_token.clear();
    }

}

DbAccess.closeConnection();

return hMapIdPath;

}

You can find an example of the content of the HashMap below:

key: p000000383
content: [t0000000000000019231, t0000000000000019232, t0000000000000019233]

key: p000000384
content: [t0000000000000019231, t0000000000000019232, t0000000000000019233]

The values that are in “content” are in the last rows in Mysql table for the same key.

    mysql> select * from token where idpath='p000003361';
+---------+------------+----------------------+------------+
| idDoc   | idSentence | idToken              | idPath     |
+---------+------------+----------------------+------------+
| d000095 | s000000048 | t0000000000000019231 | p000003361 |
| d000095 | s000000048 | t0000000000000019232 | p000003361 |
| d000095 | s000000048 | t0000000000000019233 | p000003361 |
+---------+------------+----------------------+------------+
3 rows in set (0.04 sec)

Answer 1

You need to allocate a new listFrom_token each time instead of clear()ing it. Replace this:

            listFrom_token.clear();

with:

            listFrom_token = new ArrayList<Table_token>();

Putting the list in the HashMap does not make a copy of the list. You are clearing and refilling the same list over and over.