HashMap被最后一个值覆盖 [英] HashMap overridden by last value

问题描述

Statement selectStatement = connection.createStatement();
        ResultSet selectResultSet = selectStatement.executeQuery(query);
        logger.info("sql query " + selectStatement.toString());
        ResultSetMetaData rsmd = selectResultSet.getMetaData();
        int columnsNumber = rsmd.getColumnCount();
        String[] row = new String[columnsNumber];

        int ctr = 0;
        logger.info("Reading from database...");
        while(selectResultSet.next())
        {
            for(int i=0;i<columnsNumber;i++){
                row[i] = selectResultSet.getString(i+1);
            }
            System.out.println();
            dataFromQuery.put(ctr++, row);
        }
        selectResultSet.close();

从HashMap读回时，它仅打印最后一行 n次。 p>

On reading back from HashMap, it prints only the last row 'n' number of times.

推荐答案

您缺少的是- row = new String [columnsNumber]; 在while循环中，这实际上会导致覆盖数组对象的值，并且您将同一对象添加到 HashMap 。

What you are missing is - row = new String[columnsNumber]; in while loop, which actually cause over writing array object value and you are adding same object to HashMap.

...
while(selectResultSet.next()){
     row = new String[columnsNumber];
     for(int i=0;i<columnsNumber;i++){
         row[i] = selectResultSet.getString(i+1);
     }
     System.out.println();
     dataFromQuery.put(ctr++, row);
}
...

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