Can there be a HashMap with 3 different types in Java?

Question

I have a HashMap like

Map<String, JPanel> MapItems = new HashMap<String, JPanel>();

What if I want to put third value as well in a Map or List something like this

Map<String, JPanel, JLabel> MapItems = new HashMap<String, JPanel, JLabel>();

it doesn't matter if I have to call with element position instead String Value so it isn't necessary to use Map only but if there is some other way around please tell me. I just want to put my JPanel and JLabel together.

Answer 1

Create another Object to wrap it and save the combination of your JPanel and JLabel, something like that:

public class WrapperTest {

    private JPanel jPanel;
    private JLabel jLabel;

    public WrapperTest(JPanel jPanel, JLabel jLabel) {
        super();
        this.jPanel = jPanel;
        this.jLabel = jLabel;
    }

    public JPanel getjPanel() {
        return jPanel;
    }
    public void setjPanel(JPanel jPanel) {
        this.jPanel = jPanel;
    }
    public JLabel getjLabel() {
        return jLabel;
    }
    public void setjLabel(JLabel jLabel) {
        this.jLabel = jLabel;
    }

}

And use your hash this way:

Map<String, WrapperTest> mapItems = new HashMap<String, WrapperTest>();

Example:

public class Main {

    public static void main(String[] args) throws ParseException {

        JPanel jPanel1 = new JPanel();
        JLabel jLabel1 = new JLabel();

        WrapperTest wrapper1 = new WrapperTest(jPanel1, jLabel1);

        Map<String, WrapperTest> mapItems = new HashMap<String, WrapperTest>();
        mapItems.put("key1", wrapper1);

    }

}

Answer 2

Here is another way. Make an object wrapper around JPanel and JLabel and use that as the value.

class JWrapper {
    JPanel panel;
    JLabel label;
    // Constructor, getters, setters ...
}

// ...
HashMap<String, JWrapper> map = new HashMap<String, JWrapper>();
// ...

Answer 3

No, not really.

The purpose of a map is to map from one thing to another: think of it as a source and a destination, or a label on a box and the contents of the box. There isn't room for a third "type of thing" in there.

It might be that what you really want is to map the String onto a combination of the other two; in other words, you want to look up both of the other values using the String ; you want to store two things in the box. If so, you can certainly do that, but you need to create a new Class panelAndLabel that contains the other two items. You can then use that as the value type of your HashMap .

(Or, for a quick hack, the value could be of type Object[] , or List<Object> , and then you could put what you want into the value wrapper. But, as I say, that would be a bit of a hack.)

Answer 4

Guava has a nice data structure called a Table , for exactly this purpose. Of course, another option is for you to roll your own, but I would use whats out there.