Solved Can't understand why this BlockPopulator Fails

Code:java

 
public class OrePopulator extends BlockPopulator {
 
    @Override
    public void populate(World world, Random random, Chunk chunk) {
        int X, Y, Z;
        boolean isStone;
        for (int i = 1; i < 15; i++) {  // Number of tries
            if (random.nextInt(100) < 20) {  // The chance of spawning
                X = random.nextInt(15);
                Z = random.nextInt(15);
                Y = random.nextInt(40) + 20;  // Get randomized coordinates
                if (chunk.getBlock(X, Y, Z).getType() == Material.END_STONE) {
                    isStone = true;
                    while (isStone) {
                        chunk.getBlock(X, Y, Z).setType(Material.DIAMOND_ORE);
                        if (random.nextInt(100) < 40) {   // The chance of continuing the vein
                            switch (random.nextInt(5)) {  // The direction chooser
                                case 0:
                                    X++;
                                    break;
                                case 1:
                                    Y++;
                                    break;
                                case 2:
                                    Z++;
                                    break;
                                case 3:
                                    X--;
                                    break;
                                case 4:
                                    Y--;
                                    break;
                                case 5:
                                    Z--;
                                    break;
                            }
                            isStone = (chunk.getBlock(X, Y, Z).getType() == Material.END_STONE) && (chunk.getBlock(X, Y, Z).getType() != Material.DIAMOND_ORE);
                        } else isStone = false;
                    }
                }
            }
        }
    }
}
 

The block population throws this error:

[17:17:03] [Server thread/ERROR]: Error occurred while enabling BeyondHorizons v1.0.1 (Is it up to date?)
net.minecraft.server.v1_15_R1.ReportedException: Exception initializing level
at net.minecraft.server.v1_15_R1.MinecraftServer.initWorld(MinecraftServer.java:516) ~[patched_1.15.2.jar:git-Paper-143]
at org.bukkit.craftbukkit.v1_15_R1.CraftServer.createWorld(CraftServer.java:1037) ~[patched_1.15.2.jar:git-Paper-143]
at org.bukkit.Bukkit.createWorld(Bukkit.java:536) ~[patched_1.15.2.jar:git-Paper-143]
at org.bukkit.WorldCreator.createWorld(WorldCreator.java:320) ~[patched_1.15.2.jar:git-Paper-143]
at me.slimeyderp.beyondhorizons.BeyondHorizons.makingAetherWorld(BeyondHorizons.java:80) ~[?:?]
at me.slimeyderp.beyondhorizons.BeyondHorizons.onEnable(BeyondHorizons.java:20) ~[?:?]
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:263) ~[patched_1.15.2.jar:git-Paper-143]
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:337) ~[patched_1.15.2.jar:git-Paper-143]
etc...
Caused by: java.lang.IllegalArgumentException: x out of range (expected 0-15, got 16)
at com.google.common.base.Preconditions.checkArgument(Preconditions.java:168) ~[patched_1.15.2.jar:git-Paper-143]
at org.bukkit.craftbukkit.v1_15_R1.CraftChunk.validateChunkCoordinates(CraftChunk.java:330) ~[patched_1.15.2.jar:git-Paper-143]
at org.bukkit.craftbukkit.v1_15_R1.CraftChunk.getBlock(CraftChunk.java:95) ~[patched_1.15.2.jar:git-Paper-143]
at me.slimeyderp.beyondhorizons.OrePopulator.populate(OrePopulator.java:46) ~[?:?]
at net.minecraft.server.v1_15_R1.Chunk.loadCallback(Chunk.java:680) ~[patched_1.15.2.jar:git-Paper-143]
at net.minecraft.server.v1_15_R1.PlayerChunk.lambda$null$11(PlayerChunk.java:530) ~[patched_1.15.2.jar:git-Paper-143]
etc...

( I put etc when it started to go inside the way Bukkit manages the code )

Why is it not working? Also, the world has 2 layers of purpur bricks on top and from the 3rd block down to the last one, it's all end stone, excluding the last layer, which is bedrock. I don't get where I'm screwing up.

 

Thank you!