Permissions p = new Permissions( ZERO );
Permissions p = new Permissions( EMPTY );
    public static Permissions parseString( String rwrwrw )    {    	    	Permissions p = new Permissions( ZERO );    	String regex = "([Rr_][Ww_]){3}";    	    	if ( rwrwrw == null || ! rwrwrw.matches(regex) )    		throw new ApiUsageException( "Permissions are of the form: "+regex);    	    	char c;    	    	c = rwrwrw.charAt(0);    	if ( c == 'r' || c == 'R' ) p.grant( USER, READ );    	c = rwrwrw.charAt(1);    	if ( c == 'w' || c == 'W' ) p.grant( USER, WRITE );    	c = rwrwrw.charAt(2);    	if ( c == 'r' || c == 'R' ) p.grant( GROUP, READ );    	c = rwrwrw.charAt(3);    	if ( c == 'w' || c == 'W' ) p.grant( GROUP, WRITE );    	c = rwrwrw.charAt(4);    	if ( c == 'r' || c == 'R' ) p.grant( WORLD, READ );    	c = rwrwrw.charAt(5);    	if ( c == 'w' || c == 'W' ) p.grant( WORLD, WRITE );    	        	return p;    }