Apenas números

public static String SomenteNumeros(String valor) {
        if (valor == null) return "";
        
        String result = "";
        if (valor.length() &gt 0)
            if (valor.substring(0,1).equals("-")) result = "-";
        
        for (int i = 0; i &lt valor.length(); i++)
            if ( Character.isDigit(valor.charAt(i)) )
                result = result + valor.charAt(i);
        
        return result;
    }

String x = "sg6s88snw7";
		 System.out.println(x);
		 System.out.println(x.replaceAll("[^0-9]", ""));