java.lang.NullPointerException和ResultSet(java.lang.NullPointerException and ResultSet)

 这是我的第一篇文章，请耐心等待。 我正在研究一个java项目，它连接到一个sql数据库。 我目前要做的是当我单击一个按钮时，将在我的数据库的文本区域中显示项目的名称和具有指定ID的项目的价格。 但是，当我单击该按钮时，会出现如下错误： 
 
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at OrderFrame.waterButtonActionPerformed(OrderFrame.java:494)
at OrderFrame.access$000(OrderFrame.java:11)
 
 这是我的waterButtonActionPerformed的代码： 
 
private void waterButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            
// TODO add your handling code here:
    try{

    String query;
    query = "SELECT itemName, itemPrice FROM item WHERE itemID = '11111'";
    String itemName = " ",itemPrice =" ";  

      ***ResultSet rs = st.executeQuery(query);***

       if(rs != null){
        while(rs.next())
        { 
         itemName = rs.getString(1);
         itemPrice = rs.getString(2);
        }
       orderTextArea.setText(itemName);
       orderTextArea.setText(itemPrice);
       }
         } catch (SQLException ex) {}
}        
 
 第494行是具有ResultSet声明的行。 我希望有人可以帮我解决这个问题。 先谢谢你。 

This is my first post so please be patient. I am working on a java project and that connects to a sql database. What I am currently trying to do is when I click a button, will display the name of the item and the price of the item with the specified ID in the text area from my database. However, when I click the button an error such as this appears:
 
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at OrderFrame.waterButtonActionPerformed(OrderFrame.java:494)
at OrderFrame.access$000(OrderFrame.java:11)
 
Here is the code for my waterButtonActionPerformed:
 
private void waterButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            
// TODO add your handling code here:
    try{

    String query;
    query = "SELECT itemName, itemPrice FROM item WHERE itemID = '11111'";
    String itemName = " ",itemPrice =" ";  

      ***ResultSet rs = st.executeQuery(query);***

       if(rs != null){
        while(rs.next())
        { 
         itemName = rs.getString(1);
         itemPrice = rs.getString(2);
        }
       orderTextArea.setText(itemName);
       orderTextArea.setText(itemPrice);
       }
         } catch (SQLException ex) {}
}        
 
The line 494 is the one with the declaration of the ResultSet. I am am hoping someone can help me fix this issue. Thank you in advance.

原文：https://stackoverflow.com/questions/15794369