Not working interact example

gistfile1.java

import org.bukkit.block.Block;
import org.bukkit.entity.Player;
import org.bukkit.event.Event;
import org.bukkit.event.Event.Priority;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.event.player.PlayerListener;
import org.bukkit.plugin.java.JavaPlugin;

public class Plugin extends JavaPlugin {
    
    @Override
    public void onDisable() {
        
    }

    @Override
    public void onEnable() {
        this.getServer().getPluginManager().registerEvent(Event.Type.PLAYER_INTERACT, new PlayerListener() {
            @Override
            public void onPlayerInteract(PlayerInteractEvent event) {
                Block block = event.getClickedBlock();
                Player player = event.getPlayer();
                player.sendMessage("Hit! block == null ? " + (block == null) + " cancelled ? " + event.isCancelled());
            }
        }, Priority.Normal, this);
    }
    
}