使用JDBC查询执行executeUpdate时出现空指针异常

Question

I am getting a Null Pointer Exception while executing the insert query. Everything seems to be fine but the problem still exists.

Code used for Database Connection.

public class DBConnect 
{
    static Connection c ;
    static Statement st ;
    {
        try 
        {
            Class.forName("oracle.jdbc.driver.OracleDriver");
            c=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","ashuthesmartest","ashutosha");
            st=c.createStatement();
        } 
        catch (Exception ex) 
        {
            JOptionPane.showMessageDialog(null, "Database error");
        }
    }   
}

Action Performed on Button Click

private void b3ActionPerformed(java.awt.event.ActionEvent evt) {                                   
    try 
    {
        char[] arr = pa1.getPassword() ;
        String s2 = Arrays.toString(arr) ;
        String s1 = t3.getText() ;
        DBConnect.st.executeUpdate("insert into LOGIN values('"+s1+"','"+s2+"')");   **//EXCEPTION IN THIS LINE**
    } 
    catch (Exception ex) 
    {
        ex.printStackTrace();
    }
} 

Answer 1

The initialization block in which you create the connection and the statement is not a static initialization block.

Therefore, it will only be executed when you create an instance of the class DBConnect .

Since you seem to be using DBConnect only statically, that never happens. Your initialization block should be made static. A static initialization block has the keyword static preceding the left brace:

static {
    // try etc.
}