Method isSolid

src/main/java/net/minecraft/block/material/Material.java:94–97

Returns true if the block is a considered solid. This is true by default.

()

     * Returns true if the block is a considered solid. This is true by default.
     */
    public boolean isSolid()
    {
        return true;
    }

    /**
     * Will prevent grass from growing on dirt underneath and kill any grass below it if it returns true