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