httpservices/src/main/java/ucar/httpservices/HTTPUtil.java
static public String abspath(String path)
    {
        if(path == null) return "/";
        StringBuilder b = new StringBuilder(path);
        canonicalpath(b);
        if(b.charAt(0) == '/')
            b.deleteCharAt(0);
        if(b.charAt(0) != '/' || !hasDriveLetter(b))
            b.insert(0, '/');
        return b.toString();
    }
static public String abspath(String path)
    {
        if(path == null) return "/";
        StringBuilder b = new StringBuilder(path);
        canonicalpath(b);
        if(b.charAt(0) == '/')
            b.deleteCharAt(0);
        if(b.charAt(0) != '/' || !hasDriveLetter(b))
            b.insert(0, '/');
        return b.toString();
    }
Convert path to add a  leading '/'; assumes canonical.

@param path convert this path
@return absolute version