ArrayList中的Java HashMap

Question

如何获取arrayList中的HashTable的值？

我有以下代码：

public ArrayList resultSetToArrayList(ResultSet rs) { 

    ArrayList list = new ArrayList(); 
    try { 
     ResultSetMetaData md = rs.getMetaData(); 
     int columns = md.getColumnCount(); 
     int rowcount = 0; 
     while (rs.next()) { 
      Hashtable row = new Hashtable(); 
      for (int i = 1; i <= columns; ++i) { 
       row.put(md.getColumnName(i), rs.getString(i)); 
      } 
      list.add(rowcount, row); 
      rowcount++; 
     } 
    } catch (Exception e) { 
     e.printStackTrace(); 
    } 

    return list; 
} 

Answer 1

你似乎是使用raw types和Hashtable代替HashMap的。我想你问像

public List<Map<String, String>> resultSetToArrayList(ResultSet rs) { 
    List<Map<String, String>> list = new ArrayList<>(); 
    try { 
     ResultSetMetaData md = rs.getMetaData(); 
     int columns = md.getColumnCount(); 
     while (rs.next()) { 
      Map<String, String> row = new HashMap<>(); 
      for (int i = 1; i <= columns; ++i) { 
       row.put(md.getColumnName(i), rs.getString(i)); 
      } 
      list.add(row); 
     } 
    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
    return list; 
} 

至于获得的值回了Map，你可能会迭代Map.keySet()像

for (String key : map.keySet()) { 
    System.out.printf("%s = %s%n", key, map.get(key)); 
}