My dropdownlist and List is wrong

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.WindowConstants;
 
 
public class StoreGUI extends JFrame {
 
	private static final long serialVersionUID = 1L;
	private JFrame thisFrame;
	private Container c;	
    private JPanel midPanel=new JPanel();
    
    private JPanel userPanel=new JPanel();
    private JLabel whoJL=new JLabel("Name");
    private JTextField whoJTF=new JTextField(8);
    private JLabel noJL=new JLabel("Number");
    private JTextField noJTF=new JTextField(8);
       
    private JPanel controlPanel=new JPanel();    
    JTextField txt;
 
    private JButton loginJB=new JButton("Logga in");
    private JButton logoutJB=new JButton("Logga ut");
    private JButton regJB=new JButton("Registrera ny Användare");
    private JButton addJB=new JButton("Lägg till vara");
    private JButton updateJB=new JButton("Uppdatera vara");
    private JButton removeJB=new JButton("Ta bort vara");     
    private JButton exitJB=new JButton("Exit");
 
    String category[] = {"India","Germany","America","Russia"};
    private JComboBox combo = new JComboBox(category);
 
    private String books[] = {
            ("Ant: The Definitive Guide"+"covers/ant.gif"),
            ("Database Programming with JDBC and Java"+
                          "covers/jdbc.gif"),
            ("Developing Java Beans"+ "covers/beans.gif"),
 
        };
 
     private JList booklist = new JList(books);        
 
	  
	    class AppActionListener implements ActionListener{
	        public void actionPerformed(ActionEvent ae){
	            String name=whoJTF.getText();
	            String number=noJTF.getText();
	            
	            JButton temp=(JButton)ae.getSource();
	            
	            if(temp==logoutJB){
	                System.out.println("Looking up "+name);
	                    noJTF.setText(number);
	                    noJTF.setText("Not found!");	              
	            }
	            
	            if(temp==addJB){
	                
	            }
 
	            if(temp==updateJB){
	                
	            }   
	            
	            if(temp==removeJB){
	               
	            }   
	            
	            if(temp==loginJB){           
	                whoJTF.setText("");
	                noJTF.setText("");
	            }
	            
	            if(temp==exitJB){                   
	                    System.exit(0);
	                }
	            }                        
	        }
	    
	
	
	public void showGUI() {
		
        this.setLayout(new BorderLayout());
        
        midPanel.setLayout(new FlowLayout());
        userPanel.setLayout(new GridLayout(2,2));
 
        userPanel.add(combo);        
        booklist.setVisibleRowCount(4);
        JScrollPane pane = new JScrollPane(booklist);
        userPanel.add(pane);        
        midPanel.add(userPanel);
 
        this.add(midPanel, BorderLayout.CENTER);        
        
        controlPanel.setLayout(new FlowLayout());
        loginJB.addActionListener(new AppActionListener());
        controlPanel.add(loginJB);
        logoutJB.addActionListener(new AppActionListener());
        controlPanel.add(logoutJB);
        regJB.addActionListener(new AppActionListener());
        controlPanel.add(regJB);
        addJB.addActionListener(new AppActionListener());
        controlPanel.add(addJB);    
        updateJB.addActionListener(new AppActionListener());
        controlPanel.add(updateJB);
        removeJB.addActionListener(new AppActionListener());
        controlPanel.add(removeJB);                   
        exitJB.addActionListener(new AppActionListener());
        controlPanel.add(exitJB);        
        this.add(controlPanel, BorderLayout.SOUTH);        
        this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
 
	      
	 }
	
	
	 public StoreGUI() {
 
		 this.setExtendedState(Frame.NORMAL);		 
		 thisFrame = this;
		 this.setTitle("Store");
		 this.pack();
		 this.setVisible(true);
		 thisFrame.setSize(600,600);
		 this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		 c = getContentPane();		 
		 showGUI();	 
	
	 }
 
 
		}

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