Java GUI插入图片不显示问题解决方法

public abstract class AbstractMainFrame extends JFrame {
    private JLabel titleLabel = new JLabel(new ImageIcon("fruit.jpg"));
    private JButton btn = new JButton("进入系统");
 
    private void init(){
        this.setTitle("水果超市欢迎您");
        this.setSize(600,600);
        this.setResizable(false);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
 
    private void addComponent(){
        this.add(this.titleLabel, BorderLayout.NORTH);
        JPanel btnPanel = new JPanel();
        this.add(btnPanel,BorderLayout.CENTER);
        btnPanel.setLayout(null);
        btn.setBounds(200,20,200,50);
        btnPanel.add(btn);
    }
 
 
    public AbstractMainFrame(){
        this.init();
        this.addComponent();
    }
 
}