Can you tell me is my java code connect to the oracle sql database?

[troy wu]

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

import java.sql.*;

public class Desktop extends JFrame implements ActionListener
{
	  private JLabel tit,aut;
	  private JTextField ti,au;
	  JButton b;
	  Connection conn=null; 
	  public Desktop()
	  {
		  super("Desktop");
		//create content pane
	      Container c = getContentPane();
	      c.setLayout(new FlowLayout(FlowLayout.LEFT));
	      try{
	           String userName = "system";
	           String password = "TROY0917x";
	           String url = "jdbc:oracle:thin:system@//localhost:1521/xe";         
	           Class.forName ("oracle.jdbc.driver.OracleDriver");	        
	           conn = DriverManager.getConnection(url,userName,password);       
	         }
	             catch( ClassNotFoundException x)
	               {
	                 System.out.println("Driver Exceptions");
	               
	             }
	             
	             catch(NullPointerException m)
	      {
	            	 System.out.println("Null Exceptions");
	      }
	             catch( SQLException y)
	               {
	                	  System.out.println("SQL Exceptions");
	               }
	             //create labels
	             tit = new JLabel("TITLE:",JLabel.LEFT);
                 aut = new JLabel("author:",JLabel.LEFT);
                 //create textfields
                 ti=new JTextField(30);
           	     au=new JTextField(30);
           	     //create button
           	  b=new JButton("search");
           	  //add labels and text fields to container
           	 c.add(tit);
  		     c.add(ti);
  		     c.add(aut);
  		     c.add(au);
		     c.add(b);
		   b.addActionListener(this);
           addWindowListener(new WindowAdapter(){
             public void windowClosing(WindowEvent e)
               {
                    System.exit(0);
                }
           });
           setSize(400,160);
           setVisible(true);
	                 
	  }
	  public void actionPerformed(ActionEvent ae)
	     {
	    	 if (ae.getSource() == b)
	         {
	    		 
	    		 String query="";
	    		 
	    		 if((au.getText().trim().length()>0) && (ti.getText().trim().length()>0))
	    		 {
	    			 query="select * from tbl_book where upper(author) like upper('%"+au.getText()
	    			         +"%') and upper(title) like upper('%"+ti.getText()+"%')";
	    			 
	    		 }else if(au.getText().trim().length()>0){
	    			 query="select * from tbl_book where upper(author) like upper('%"+au.getText()+"%')";
	    		 }else if(ti.getText().trim().length()>0){
	    			 query="select * from tbl_book where upper(title) like upper('%"+ti.getText()+"%')";
	    		 }else{	    			
	    			 System.out.println("Please Enter Title/Author or Both");
	    			 return;
	    		 }
	    		 
	    		 Statement stmt=null;
	    		 ResultSet rs=null;
	    	 try{	
	    		 //System.out.println("query is "+query);
	    		 stmt = conn.createStatement();
	    		 rs = stmt.executeQuery(query);
	    	int i=1;    	    	    	    	
	          while(rs.next())
	                {	                
	        	  System.out.println("record "+i);
	        	  		System.out.println("-------------------------------------------------");
	        	  	
	              		System.out.println("Isbn :"+rs.getString("isbn")+" \n Title :"+rs.getString("title")
        +" \n Author :"+rs.getString("author")+"\n publisher :"+rs.getString("publisher")+" \n Year :"+rs.getDate("year"));
	        	  		System.out.println("---------------------------------------------");
	               i++;
	                }
	          if(i==1)
	        	  System.out.println("No Records Found In Database");
	          
	    	    
	          rs.close();
              stmt.close();
              conn.close();
	                }
	                 catch(SQLException ex){	    
	                   System.out.println("Exceptions");
	                   	                   
	                 }
	                 
	                 } 
}
	     public static void main(String args[])
	        {  
	    	 
	    	Desktop des = new Desktop();
	    	des.setTitle("My desktop");
	    	
	 	     }
	 }

when I run this with esclipe, it will appear "SQL EXCEPTION" ON THE CONSOLE WINDOW BELOW. however, there will be a search window appear.  whenever I type something inside and search, i always get  tons of red lines. like this:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Desktop.actionPerformed(Desktop.java:90)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

[Jesper de Jong]

Most likely the variable conn is null when the running program reaches line 90.

Check the console output. Do you see a message such as "Driver Exceptions", "Null Exceptions" or "SQL Exceptions" - the error messages your code prints in the constructor? Maybe something fails in the constructor so that conn stays null.

[Tim Moores]

Instead of printing out fixed strings in the catch block that tell you just about nothing about what went wrong, print the stack trace of all exceptions like "ex.printStrackTrace()".

[troy wu]

Jesper de Jong wrote:Most likely the variable conn is null when the running program reaches line 90.

Check the console output. Do you see a message such as "Driver Exceptions", "Null Exceptions" or "SQL Exceptions" - the error messages your code prints in the constructor? Maybe something fails in the constructor so that conn stays null.

I think the oracle database hasnot connected to Esclipe ide. I have been trying connect oracle database to Esclipe for two days, and I also done some research on the web, but I have not idea why the oracle cannot connect to the ide. I am gonna ask my professor tomorrow at school,. ty

[Campbell Ritchie]

Please show what happens when you connect to the database via the command line.
It isn't right to connect to databases from inside a GUI class. You shou‍ld be able to connect to the database without any GUIs and the GUI classes are only there for displaying the results.