public class Jump extends JavaPlugin implements Listener {
    public void onEnable(){
        getServer().getPluginManager().registerEvents(this, this);
    }

    @EventHandler
    public void onPlayerToggleFlight(PlayerToggleFlightEvent event){
       Player player = event.getPlayer();
       if (player.getGameMode() == GameMode.CREATIVE)
           return;
       event.setCancelled(true);
       player.setAllowFlight(false);
       player.setFlying(false);
       player.setVelocity(player.getLocation().getDirection()
               .multiply(1.5).setY(1));

    }

    @EventHandler
    public void onPlayerMove(PlayerMoveEvent event) {

        Player player = event.getPlayer();
        if ((player.getGameMode() != GameMode.CREATIVE)
                && (player.getLocation().subtract(0, 1, 0).getBlock().getType() != Material.AIR)
                && (!player.isFlying()))
            player.setAllowFlight(true);


    }
}