Setting block at location

I'm trying to use a command to set a player inside a glass box. So far this is what I've tried. I tried getting the players location and its X, Y, Z and adding or subtracting it based on what I needed, I used double's to do that. I'm not sure how to set the block at those locations. Here is the code I've tried.

Code:

    public void freeze(Player player) {
        Location location;
        double xpos = player.getLocation().getX() + 1.0;
        double xneg = player.getLocation().getX() - 1.0;
        double y = player.getLocation().getY() + 3;
        double zpos = player.getLocation().getZ() + 1.0;
        double zneg = player.getLocation().getZ() - 1.0;
    }

now I dont know how to use what I have to spawn the blocks. Any help, thread, pseudo code or even actual code snippets would be appreciated (But dont spoon feed me, I actually want to learn this for future reference). Thanks in advance!

 

World#getBlockAt(Location).setType(Material);