Weird tiled effect with calculating Normals, TRIANGLE_STRIPS

[Ziath]

I've made a height map program and i'm trying to calculate normals for each vertex. I've tried searching for a solution all morning but i can not figure out the error in my code. I am getting a weird tiled effect as you can see in the picture below.. I'm using triangle strips to render a 400 by 400 vertice plane. I have set all y values to 0 for this post. If anyone could help, and point out whats wrong, that would be awesome

http://imgur.com/ICeksXX

public void calculateNormals() {
	
		for (int n = 0; n < 400*200; n++) {
			float x1 = vBuffer.get(n + 0);
			float y1 = vBuffer.get(n + 1); 
			float z1 = vBuffer.get(n + 2);	
				
			float x2 = vBuffer.get(n + 3); 
			float y2 = vBuffer.get(n + 4); 
			float z2 = vBuffer.get(n + 5); 
				 
			float x3 = vBuffer.get(n + 6); 
			float y3 = vBuffer.get(n + 7);
			float z3 = vBuffer.get(n + 8); 
				
			float Ux = (x2 - x1);
			float Uy = (y2 - y1);
			float Uz = (z2 - z1);
				
			float Vx = (x3 - x1);
			float Vy = (y3 - y1);
			float Vz = (z3 - z1);

			float Nx = Uy*Vz - Uz*Vy;
			float Ny = Uz*Vx - Ux*Vz;
			float Nz = Ux*Vy - Uy*Vx;
				
			float normLength = (float)Math.sqrt(Math.pow(Nx,2) + Math.pow(Ny,2) + Math.pow(Nz,2));
			if(normLength == 0){
				Nx = 0;
				Ny = 0;
				Nz = 0;
			}else{
				Nx /= normLength;
			    Ny /= normLength;
			    Nz /= normLength;
			}
			
			if ((n %2)==0){
				
				nBuffer.put(Nx).put(Ny).put(Nz);
				
			}
			else{
				
				nBuffer.put(-Nx).put(-Ny).put(-Nz);
				
			}
			
		
		}
	
		this.nBuffer.flip();
	}

[Fool Running]

the n++ in your loop looks suspicious. It looks like it should be += 3.

P.S. Math.pow(Nx,2) is a lot slower then Nx * Nx.

[quew8]

For the record it is a pretty cool effect. I would just keep it as bugs influencing design style. If you want rid of it, I second @Fool Running.

For the record I would also recommend using LWJGL's vector classes or writing your own, it makes higher level maths so much easier. (I know this isn't really high level but...)