未在实现类中实现的EventListener接口中的handleEvent方法

Question

EventListener interface declares handleEvent(Event evt) method, and in the code below GeneratorListener extends that interface. I am told this code is correct. BUT I don't see why Printer class does not have to implement handleEvent method? Isn't it the case that all the methods in an interface must be implemented?

public interface GeneratorListener extends EventListener {
    void objectGenerated(String object);
}

public class Printer implements GeneratorListener { 
    public void objectGenerated(String object) {
        System.out.println(object);
    }
}

Answer 1

Seems I know the answer. Method

public void handleEvent(Event evt);

is contained in org.w3c.dom.events.EventListener. But in your GeneratorListener interface you probably imported java.util.EventListener that looks like

package java.util;

/**
 * A tagging interface that all event listener interfaces must extend.
 * @since JDK1.1
 */
public interface EventListener {
}

So your Printer class implements the only abstract method that you have in Printer class hierarchy. That's why your code is correct.