@EventHandler(priority = EventPriority.HIGH)
public void spawnmove(PlayerRespawnEvent event) {

    if (!event.isBedSpawn()) {
        Location curloc = event.getRespawnLocation();
        boolean look = true;
        int lookcount = 0;
        World wld = getServer().getWorld(this.getConfig().getString("worldName"));
        while (look) {

            Integer xloc = ((int) (rand.nextInt(230) - 100   curloc.getX()));
            if (xloc > 2200){
                xloc = xloc - 3400;
            }
            if (xloc < -1200){
                xloc = xloc   3400;
            }
            Integer zloc = ((int) (rand.nextInt(300) - 100   curloc.getZ()));
            if (zloc < -2400){
                zloc = zloc   6000;
            }
            if (zloc > 3600){
                zloc = zloc - 6000;
            }
            Integer yloc = wld.getHighestBlockYAt(xloc, zloc);
            Material mat = wld.getBlockAt(xloc, (yloc - 1), zloc).getType();

            if ((mat == Material.GRASS) || (mat == Material.SAND) || (mat == Material.HARD_CLAY)) {
                look = false;
                wld.setSpawnLocation(xloc, yloc, zloc);
                this.getLogger().info(
                        "spawn moved "   xloc.toString()   ":"   yloc.toString()   ":"   zloc.toString());
            }
            lookcount  ;
            if (lookcount > 100) {
                this.getLogger().info("spawn not moved");
                look = false;
            }
        }

    }
}

EDIT: Made better by psygate