ArrayList <Object <ArrayList <Object> >>

Question

即時嘗試放置在我的Arraylist對象與ArrayList對象，但它不工作在這裏是我的代碼。 我得到的錯誤錯誤：空 顯示java.lang.NullPointerException：我LINE

mi.get(i).comments.add(new komments());

它應該工作，因爲我= 0和mi.get（我）應該存在

ArrayList<dateiles> mi = new ArrayList<dateiles>(); 

try { 
    st = con.createStatement(); 
    rs = st.executeQuery("SELECT * FROM BE"); 
    int i = 0; 

    while (rs.next()) { 

     mi.add(new dateiles()); 
     mi.get(i).be = rs.getString("BEBE"); 
     mi.get(i).name = rs.getString("BEBENAME"); 

     mi.get(i).besid = rs.getInt("BEID"); 

     /** 
     * 
     * kommentsquery 
     * 
     */ 
     st2 = con.createStatement(); 
     rs2 = st2.executeQuery("SELECT * FROM COMMENTS WHERE BEID='" + mi.get(i).besid + "' "); 
     int i2 = 0; 
     while (rs2.next()) { 
      mi.get(i).comments.add(new komments()); 
      mi.get(i).comments.get(i2).name = rs2.getString("ONAME"); 
      mi.get(i).comments.get(i2).comment = rs2.getString("COMMENT"); 
      i2++; 
     } 

     i++; 
    }