Java APIs

Sometimes it is pretty handy to pass through functions to other functions (as is done in functional languages). Such a feature should also exist in Java. These functions could heavily simplify eventhandlers and other listeners, eventually even thread development can be simplified like this. The following illustrates what I mean:

Old non-functional implementation

class SomeFrame extends Frame {
    Button button = new Button(...);
    SomeFrame {
        ...
        button.addActionListener(new ActionListener(this) {
            public void actionPerformed(ActionEvent e) {
                buttonClicked(e)
            }
        });
        ...
    }

    public void buttonClicked(ActionEvent e) {...}    
}

Functional implementation, much simpler:

class SomeFrame extends Frame {
    Button button = new Button(...);
    SomeFrame {
        ...
        button.addActionEvent(function this.buttonClicked);
        ...
    }

    public void buttonClicked(ActionEvent e) {...}    
}

// Somewhere in Button should be:

...
    void addActionEvent(void function(ActionEvent), func) {...}
...

It should then also be possible to make collections out of functions.

Suggestions please...