public void itemAttributeModifier(ItemAttributeModifierEvent event) {
ItemStack stack = event.getItemStack();
Item item = stack.getItem();
if (item == Items.DIAMOND_SWORD) {
stack.addAttributeModifier(Attributes.ATTACK_DAMAGE, new AttributeModifier("damage", 1.0D, AttributeModifier.Operation.MULTIPLY_BASE), EquipmentSlotType.MAINHAND);
}
}
It continues to call the addAttributeModifier infinitely. In game, the tooltip ends up just overflowing with attribute modifiers.