DimTeleporter.java

package com.crashdbo.firstmod.util.commands;

import javax.annotation.Nonnull;

import net.minecraft.entity.Entity;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.entity.player.EntityPlayerMP;
import net.minecraft.server.MinecraftServer;
import net.minecraft.util.math.BlockPos;
import net.minecraft.world.Teleporter;
import net.minecraft.world.WorldServer;

public class DimTeleporter extends Teleporter{

    public DimTeleporter(WorldServer worldIn, double x, double y, double z) {
        super(worldIn);
        this.worldServer = world;
        this.x = x;
        this.y = y;
        this.z = z;
    }

    private final WorldServer worldServer;
    private double x;
    private double y;
    private double z;

    @Override
    public void placeInPortal(@Nonnull Entity entity, float rotationYaw) {
        // The main purpose of this function is to *not* create a nether portal
        this.worldServer.getBlockState(new BlockPos((int) this.x, (int) this.y, (int) this.z));

        entity.setPosition(this.x, this.y, this.z);
        entity.motionX = 0.0f;
        entity.motionY = 0.0f;
        entity.motionZ = 0.0f;
    }

    public static void teleportToDimension(EntityPlayer player, int dimension, double x, double y, double z) {
        int oldDimension = player.getEntityWorld().provider.getDimension();

        if (player.world.isRemote) {
            EntityPlayerMP entityPlayerMP = (EntityPlayerMP) player; //Game crashes here can't cast EntityPlayerSP to EntityPlayerMP

            MinecraftServer server = player.getEntityWorld().getMinecraftServer();
            WorldServer worldServer = server.getWorld(dimension);
            player.addExperienceLevel(0);

            if (worldServer == null || worldServer.getMinecraftServer() == null){ //Dimension doesn't exist
                throw new IllegalArgumentException("Dimension: "+dimension+" doesn't exist!");
            }

            worldServer.getMinecraftServer().getPlayerList().transferPlayerToDimension(entityPlayerMP, dimension, new DimTeleporter(worldServer, x, y, z));
            player.setPositionAndUpdate(x, y, z);
            if (oldDimension == 1) {
                // For some reason teleporting out of the end does weird things. Compensate for that
                player.setPositionAndUpdate(x, y, z);
                worldServer.spawnEntity(player);
                worldServer.updateEntityWithOptionalForce(player, false);
            }
        }


    }

}