Solved How to make a random, smoothed custom terrain?

Look at this weird world I have just created:


Each chunk is a small plains terrain and they are all seperated. But my first thought wasn't that. I wanted to make a custtom world generator which makes a simple, random plains just like Vanilla. So I made some code like this:

Code:

public class ChunkGen extends ChunkGenerator {
    public static Random r = new Random(System.nanoTime());
    private int roundup = 0;
    int[][] heightMap = new int[16][16];

    private int bilinearInterpolation(int x, int z) {
        float res = 1f / 255f * (
                heightMap[0][0] * (15-x) * (15-z) +
                heightMap[15][0] * x * (15-z) +
                heightMap[0][15] * (15-x) * z +
                heightMap[15][15] * x * z
        );
        return (int) res;
    }

    @Override
    public ChunkData generateChunkData(World world, Random random, int x, int z, BiomeGrid biome) {
        ChunkData temp = createChunkData(world);
        PerlinNoiseGenerator gen = new PerlinNoiseGenerator(random);
        heightMap[0][0] = (int) Math.round(gen.noise(0, 0)*30+1);
        heightMap[15][0] = (int) Math.round(gen.noise(15, 0)*30+1);
        heightMap[0][15] = (int) Math.round(gen.noise(0, 15)*30+1);
        heightMap[15][15] = (int) Math.round(gen.noise(15, 15)*30+1);
        for (int i = 0; i < 16; i++)
            for (int j = 0; j < 16; j++) {
                if (!((i==0 && j==0) || (i==0 && j==15) || (i==15 && j==0) || (i==15 && j==15)))
                    heightMap[i][j] = bilinearInterpolation(i,j);
                temp.setBlock(i, heightMap[i][j], j, Material.GRASS);
                temp.setBlock(i, heightMap[i][j]-1, j, Material.DIRT);
                for (int k = heightMap[i][j]-2; (k>heightMap[i][j]-6 && k>0); k--) temp.setBlock(i, k, j, Material.STONE);
                Material mt = null;
                for (int k = heightMap[i][j]-6; k>0; k--) {
                    roundup = (int) (Math.round(gen.noise(i, j)+1)*9+1);
                    switch (roundup) {
                    case 9: mt = Material.DIAMOND_ORE;
                    case 1: mt = Material.STONE;
                    case 2: mt = Material.LAPIS_ORE;
                    case 3: mt = Material.STONE;
                    case 4: mt = Material.COAL_ORE;
                    case 5: mt = Material.IRON_ORE;
                    case 6: mt = Material.REDSTONE_ORE;
                    case 7: mt = Material.STONE;
                    case 8: mt = Material.IRON_ORE;
                    case 10: mt = Material.STONE;
                    default: mt = Material.STONE;
                    }
                    temp.setBlock(i, k, j, mt);
                }
                temp.setBlock(i, 0, j, Material.BEDROCK);
            }
        return temp;
    }
}

But I don't know to connect the chunks up to make a complete, smooth and infinite terrain.
Any ideas for this please???

SOLVED: I realized everything! I am so inspired now and I am writing a World Generator Plugin Tutorial for everyone wants to make a custom world...