How can i make a structure generate only once?

i want to make a structure which generates only once and not everytime a new chunk is beeing generated.

i got the code to work but the problem is i used a variable to check if the structure is already generated.

but when i exit the game it resets the variable and the structure is beeing generated again.

so can i write the variable to NBT or something?

or is there another way to save variables in for example in my baseclass or CommonProxy?

I tried to make a new WorldSavedData class but i cant firgure out how it works.

can someone explain it to me pls?

i can't find anything about it on the internet to.

perhaps make a file???

the world save data way looks a lot easier to me then making a file.

and since it is already implemented into minecraft i think im gonna go with that one.

but do i need to register it or something?

i cant find anything about it.

i did that but it wont save.

i set my variable to true and when i restart the game it is false again.

if(world.loadItemData(WorldSaveData.class, "LegendzWorldSaveData") == null){
		WorldSavedData data = new WorldSaveData("LegendzWorldSaveData");
		world.setItemData("LegendzWorldSaveData", data);
	}

	WorldSaveData worldSaveData = (WorldSaveData) world.loadItemData(WorldSaveData.class, "LegendzWorldSaveData");


	System.out.println(worldSaveData.alreadyGenerated[0]);

i put this in the generate method in my WorldGenerator.

and here is my WorldSaveData Class

package legendz.common;

import net.minecraft.nbt.NBTTagCompound;
import net.minecraft.world.World;
import net.minecraft.world.WorldSavedData;
import net.minecraft.world.storage.MapStorage;

public class WorldSaveData extends WorldSavedData {

public static boolean[] alreadyGenerated = new boolean[8];

public WorldSaveData(String par1Str) {
	super(par1Str);
}

@Override
public void readFromNBT(NBTTagCompound nbt) {
	for(int i = 0; i < alreadyGenerated.length; i++){
		alreadyGenerated[i] = nbt.getBoolean("generated"+i);
	}
}

@Override
public void writeToNBT(NBTTagCompound nbt) {
	for(int i = 0; i < alreadyGenerated.length; i++){
		nbt.setBoolean("generated"+i, alreadyGenerated[i]);
	}
}

}