Event Example by Ocean

    @EventHandler
    // Call this event when a block is broken.
    public void onBlockBreak(BlockBreakEvent e) {

        // Get the player.
        Player p = e.getPlayer();

        // A switch statement is basically a large if statement,
        // so the switch gets the type, and then "case DIAMOND_SWORD" means
        // "if (p.getItemInHand().getType().equals(Material.DIAMOND_SWORD)) {}".

        switch (p.getItemInHand().getType())  {
        //  If it's a diamond sword then do stuff.
            case DIAMOND_SWORD:
                // Do  that stuff here

                // Don't forget your break; so that it won't continue the in switch statement after it finds the correct one (or default at the bottom there).
                break;

            case IRON_SWORD:
                // Do stuff here if it's an iron sword, you can add as many cases as you'd like.
                break;

                // The "default" is what happens if none of the above cases are correct,
                // so if they broke a block and were holding sponge you want to put what you want to happen here.
                // In this case it just breaks out and does nothing.
            default:
                break;
        }
    }