哪个对一个课堂中的多个动作更好？ 匿名内部类还是if语句在actionPerformed（）中？

Question

I am working on making menus in a java JFrame. I've seen two ways of having different responses to different events in the same class. One is to use anonymous inner classes as described in this answer from a few years ago: https://stackoverflow.com/a/10472395/5960074

public static void createMenuBar()
{
    //Main Menu Items

    menubar.add(fileMenu);
    MainWindow.window.setJMenuBar(menubar);

    //Sub menu items
    saveItem = new JMenuItem("Save");
    loadItem = new JMenuItem("Load");

    //Add to the "File" menu item
    fileMenu.add(saveItem);
    fileMenu.add(loadItem);

    //Anonymous Inner classes for actionListeners


    //Action event for saving
    saveItem.addActionListener(new ActionListener(){ //adding the listener
        @Override
        public void actionPerformed(ActionEvent e){ //creating the specific action for save
            System.out.println("You tried to save.");
        }
    });

}

In my code it looks like this and it works (as in at this point it prints "You tried to save." to the console).

I've seen other people implement ActionListener in the class and then in the method actionPerformed() they use if statements that track the source of the event. So there is one event but the code changes on what triggers it.

The first method seems messy and the second easier to read. Is there a reason to do the first method over the second?

Thanks.

Answer 1

Use the Action class with non-anonymous classes (they can be static inner classes though). It gives you nice encapsulation, makes the code readable and is in many ways better than using ActionListener .

Answer 2

First, avoid using static , you really (really) don't need it, it promotes bad code design.

Assuming you use Java 8, and thus can use lambda's:

public void createMenuBar() {
   ...
   saveItem.addActionListener(this::save);
   loadItem.addActionListener(this::load);
} 

private save(ActionEvent e) { 
    .... 
}

private load(ActionEvent e) { 
   .... 
}

If you cannot use lambdas using inner classes is better than implementing the interface and using if statements.

 public class MyGui {
     private class SaveAction implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
           ....
        }
    }

     private class LoadAction implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
           ....
        }
    }

 public void createMenuBar() {
   ...
   saveItem.addActionListener(new SaveAction());
   loadItem.addActionListener(new LoadAction());
 } 
}