CoreCorn

public class CropCorn extends CoreDoubleCrop
{
    public static final PropertyInteger AGE = PropertyInteger.create("age", 0, 4);

    private Item seed;
    private Item crop;

    public CropCorn(String name)
    {
        super(name + "_plant");
        this.seed = new CoreSeedFood(name, 3, this);
        this.crop = seed;
    }

    @Override
    protected int getBonemealAgeIncrease(World world)
    {
        return MathHelper.getInt(world.rand, 1, 3);
    }

    @Override
    public Item getSeed()
    {
        return seed;
    }

    @Override
    public Item getCrop()
    {
        return crop;
    }

    @Override
    public int getMaxAge()
    {
        return 4;
    }

    @Override
    public boolean isMaxAge(IBlockState state)
    {
        return getAge(state) >= getMaxAge();
    }

    @Override
    public AxisAlignedBB getBoundingBox(IBlockState state, IBlockAccess source, BlockPos pos)
    {
        return FULL_BLOCK_AABB;
    }

    @Override
    protected PropertyInteger getAgeProperty()
    {
        return AGE;
    }

    @Override
    protected BlockStateContainer createBlockState()
    {
        return new BlockStateContainer(this, new IProperty[] {AGE, HALF});
    }
}