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How to order by with result set? – Phpmyadmin

I want to make a leaderboard with SQL.
So I have to ORDER BY with kills in my case to get the results sorted.

But with the result set, the order is wrong. 

HashMap<String, Integer> player_list = new HashMap<>();
preparedStatement = this.pvpBox.getDtb().getConnection().prepareStatement(
    "SELECT player_name, kills FROM players ORDER BY kills DESC LIMIT 10");
ResultSet resultSet = preparedStatement.executeQuery();

while (resultSet.next()) {
    player_list.put(resultSet.getString("player_name"), resultSet.getInt("kills"));
}

No error message.

I’ve already tried in the “SQL” section of PHPMyAdmin and I’m getting the expected result..

Table example :

    player_name     kills
    player1         40
    player2         20
    player3         50
    player4         10
    player5         30

Actual result :

    player_name     kills
    player5         30
    player1         40
    player4         10
    player2         20
    player3         50

Expected result :

    player_name     kills
    player3         50
    player1         40
    player5         30
    player2         20
    player4         10

I’m using Java 8 and Apache 2.

Solution : Use the LinkedHashMap instead of HashMap (hashmap does not have any order).

Tags:

3

Answers


  1. 0

    That player_list you are using is quite obviously not a List. With the put() method and two arguments, it looks like a Map.

    If what you use is a HashMap, no wonder the order is arbitrary – HashMap does not retain any kind of ordering.

    You might want a LinkedHashMap, or another data structure altogether, like a custom object that you then actually store in a list, not in a map.

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  2. 0

    I think the problem is with the player_list which is a non-sorted map implementation. If you want to preserve the order of inserts in the map, use LinkedHashMap.

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  3. 0

    Is player_list a hashmap object? Hashmap does’nt maintain the order of the values inserted.Instead try using LinkedHashMap or TreeMap.

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