Using multiple JButtons with the same label in Java

Question

I have two buttons in my project that both have a \"+\" label. When the actionPerformed() method is called, it calls a specific method based on the label. How can I distigui

Answer 1

You shouldn't have a single listener handle the behavior for different responsibilities. If the two + buttons do not do the same thing, give the buttons separate listeners.

This will allow your code to be a lot more cohesive. By reducing your listeners to 1 responsibility each, you'll be able to re-use those responsibilities. It also make testing easier, allowing you to test each behavior in complete isolation.

Although if you must, ActionEvent#getSource() returns which ever component triggered the event. Doing a reference comparison will allow you to determine which object triggered the event.

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The best way to handle this would to separate the responsibilities your current listener has into separate classes:

class FirstListener implements ActionListener {
    @Override
    public void actionPerformed(ActionEvent e) {

    }
}

Lets assume FirstListener represents your first + button behavior. If that behavior requires any external objects (such as a field in a different class), simply pass it through the constructor:

class FirstListener implements ActionListener {
    private Object dependency;

    public FirstListener(Object dependency) {
         this.dependency = dependency;
    }

    //actionPerformed declaration
}

You can do the same for the other buttons (for example, the second + button).

If you feel this is a bit excessive, feel free to use lambda expressions to declare the listeners:

//Java 8+
button.addActionListener(event -> {

});

This doesn't give you the same modularity as the previous example, as the behavior is no longer separated from the actual class: you will be forced to change the implementation to change the behavior, rather than using dependency inversion to simply pass a different object which also implements ActionListener.