SwordItemBase 
为剑添加 onSwingHand(ItemStack itemtack, World world, double x, double y, double z) 方法。
示例:
public class YourSword extends SwordItemBase {
public YourSword() {
super(...)
}
@Override
public boolean onSwingHand(ItemStack itemtack, World world, double x, double y, double z) {
boolean ret_val = super.onSwingHand(itemtack, world, x, y, z);
//Execute when player swing hand with this sword.
return ret_val;
}
}