Game only targets one entity when more than one have the same UUID

Skylinerw please convert my UUID Pairing now. To prove that it WILL work.

I know you shouldn't mess with the UUID's because it messes with the game codes now that it means Universally Unique Identification, but I thought that they could find a way around it, I know nothing about programming in general, just basic calling methods and variables etc. but I wonder if they could, I don't know, identify when there are two entities with the same UUID and maybe set one's UUID to a randomly generated one, or not allowing the player to summon an entity whit a pre-existing UUID instead of glitching the system or crashing the game (I thought it would do so).

Also, UUIDLeast and UUIDMost is not something exclusive to 1.9, I never heard it in entities before but I know you can give UUIDLeast's and UUIDMost's to Attribute Modifiers, before any 1.9 snapshot.

Command Fix: "/summon ArmorStand ~ ~1 ~ {Invulnerable:1,NoGravity:1,ArmorItems:[{},{},{},{id:skull,Damage:1,Count:1}],UUIDLeast:0l,UUIDMost:1152921504606846976l,PersistanceRequired:1,DissabledSlots:2039583}". Now that command should work with this: "/execute @e[type=Skeleton] ~ ~ ~ summon Snowball ~ ~2 ~ {Invulnerable:1,ownerName:"10000000-0000-0000-0000-000000000000"}". The skeleton should shoot the armor stand and that is it.

"UUIDLeast" AND "UUIDMost" SEEMS to be exclusive in MC 1.9 because "UUID" is no longer supported. See my comment above for more details. That skeleton will shoot the armor stand and fight with it.

Also ENTITIES HAVE "UUIDLeast" AND "UUIDMost". For items: "/summon Item ~ ~1 ~ {Age:-32768,Invulnerable:1,Item:{id:diamond_sword,Count:1,tag:{Unbreakable:1,AttributeModifiers:[{AttributeName:"generic.attackSpeed",Name:"generic.attackSpeed",Amount:1024,Operation:0,UUIDLeast:894654,UUIDMost:2872,Slot:"mainhand"},{AttributeName:"generic.attackDamage",Name:"generic.attackDamage",Amount:2147483647,Operation:0,UUIDLeast:1,UUIDMost:1,Slot:"mainhand"}],display:{Name:"Spam-Clicking Sword","Lore:["You can spam click again."]}}}}}".

So that is why I do this. So I can recreate CrushPixel's entity targeting thing. So please upgrade and use my commands in here.

"UUIDLeast" and "UUIDMost" have existed for a very long time on entities and were the preferred tags to use. The "UUID" tag was deprecated and should not have been used because of that (which then resulted in its expected deletion for 1.9).

Regardless, this ticket is invalid. You cannot expect two of the same universally-unique identifier to function correctly. 1.9 has even introduced methods to prevent duplicate entities from existing (if two entities with a duplicate UUID exist when a chunk is loaded, all duplicate entities will be completely deleted), and /summon can no longer create more than one entity with the same UUID.

See here for more info UUIDs: https://en.wikipedia.org/wiki/Universally_unique_identifier

UUIDLeast and UUIDMost are decimal values that are converted to hexadecimal and are literally placed next to each other:

Most 2 = 00000000-0000-0002
Least 1 = 0000-000000000001
Result: 00000000-0000-0002-0000-000000000001

@Skylinerw Sorry for late response, but how to convert UUID i.e. "/summon SnowMan ~ ~1 ~ {Invulnerable:1,UUIDLeast:1l,UUIDMost:2l,Tags:["Test"],PersistanceRequired:1,DeathLootTable:"minecraft:chests/end_city_treasure",Motion:[0.06],Rotation:[90f],ActiveEffects:[{Id:11,ShowParticles:0b,Duration:2147483647}]}".

Then for it's own projectiles to hit itself (it will fight with itself). Command: "/execute @e[type=SnowMan] ~ ~ ~ summon Snowball ~ ~2 ~ {Invulnerable:1,Motion:[0.0,-9.99,0.0],ownerName:"00000000-0000-0002-0000-000000000001"}". Btw how do you reformat things you type here into code.

What if you try to summon an entity with same UUID?: "/summon MinecartRideable ~ ~1 ~ {CustomName:"I Have same UUID as my passanger",Invulnerable:1,Passangers:[{id:ArmorStand,CustomName:"I have same UUID as my vehicle",CustomNameVisible:1,UUIDLeast:1l,UUIDMost:1l,Invulnerable:1,NoGravity:1,ArmorItems:[{},{},{},{id:skull,Damage:1,Count:1}],PersistanceRequired:1,DissabledSlots:2039583}],UUIDLeast:1l,UUIDMost:1l,Tags:["Crafter_Minecart"],CustomDisplayTile:1,DisplayTile:crafting_table}".

I mean if you do that in 1.9 as 1.9 won't allow you to do that (This uses the "Passangers" tag). On success summons minecart which looks like crafting table.

Tested it and both entities vanish. This can be useful to make entities despawn using /entitydata.

@No Name1, You cannot use /entitydata to change an entity's UUID, as the "UUIDLeast" and "UUIDMost" tags are specifically removed from input from /entitydata.

Ok, whatever.

@No Name1, Please refrain from trolling Mojira reports. You are only serving to hinder Mojang's ability to fix bugs and moderator's ability to assess them.

@unknown, UUIDLeast and UUIDMost store both long variable types. However like you said this is very likely invalid and also fixed with the 1.9 snapshots

Duplicates MC-44904

Ok, maybe this ticket is invalid, but because no Kumasasa or whatever has seen this report, I'll just keep adding information to it.

I discovered another error (I didn't expect this to work properly), in the first video attached to this report, I tried to kill two Creepers with the same UUID, and only the first one summoned got killed, right? Now I've found out that if you summon two different entities, like a Spider and a Creeper, being the Creeper summoned before the Spider, and you try to kill the Creeper, the Creeper, doesn't die but the SPIDER does. I attached a new video to this report so you can see it better.

@Marcono1234, "Decimal" is a numeral system, not a datatype.

@Marcono1234 Relates to*

@No Name1 Summoning Item Frames to crash your game is an old trick m8, try doing something useful instead of trolling Mojira reports.

@No Name1 How do I know a player's UUID?

@No Name1 Typing

/say @e[r=1]

didn't work, it only said my name (get the reference?)
Also, can you explain me the difference between UUID and UUIDLeast and UUIDMost?