在《JAVA核心编程》中，有一段这样的代码

import javax.swing.*;
import java.awt.*;
import java.io.File;

public class ImageViewer {
    public static void main(String[] args){
        EventQueue.invokeLater(() -> {
            JFrame frame = new ImageViewerFrame();
            frame.setTitle("ImageViewer");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);

        });
    }
}
class ImageViewerFrame extends JFrame{
    private JLabel label;
    private JFileChooser chooser;
    private static final int DEFAULT_WIDTH = 300;
    private static final int DEFAULT_HEIGHT = 400;

    public ImageViewerFrame(){
        setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);

        label = new JLabel();
        add(label);

        chooser = new JFileChooser();
        chooser.setCurrentDirectory(new File("."));

        JMenuBar menuBar = new JMenuBar();
        setJMenuBar(menuBar);
        JMenu menu = new JMenu();
        menuBar.add(menu);

        JMenuItem openItem = new JMenuItem("open");
        menu.add(openItem);
        openItem.addActionListener(Event -> {
            int result = chooser.showOpenDialog(null);

            if (result == JFileChooser.APPROVE_OPTION){
                String name = chooser.getSelectedFile().getPath();
                label.setIcon(new ImageIcon(name));
            }
        });

        JMenuItem exitItem = new JMenuItem("exit");
        menu.add(exitItem);
        exitItem.addActionListener(Event -> System.exit(0));
    }
}

可以看到两处这样的代码

() -> {
            JFrame frame = new ImageViewerFrame();
            frame.setTitle("ImageViewer");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);

        }

Event -> {
            int result = chooser.showOpenDialog(null);

            if (result == JFileChooser.APPROVE_OPTION){
                String name = chooser.getSelectedFile().getPath();
                label.setIcon(new ImageIcon(name));
            }

不知道 -> 这个符号是什么意思，百度了一下，也没有查到