OK man...
entonces ahi esta:
public String dominioUrl(String cad){
int i,index=-1;
String cadRet="";
cad = cad.replaceAll(" ","~");
String vecCad[] = cad.split("~");
Pattern p = Pattern.compile("^([0-9a-zA-Z]([_.w]*[0-9a-zA-Z])*([0-9a-zA-Z][-w]*[0-9a-zA-Z].)+([a-zA-Z]{2,9}.)+[a-zA-Z]{2,3})$");
Matcher m;
for(i=0;i<vecCad.length;i++){
m = p.matcher(vecCad[i]);
if(m.find()){
index = i;
break;
}
}
if(index != -1){
for(i=0;i<vecCad.length;i++)
if(index != i)
cadRet += vecCad[i] + " ";
else
cadRet += "<a href=\"" + vecCad[i] + "\">" + vecCad[i] + "</a> ";
}else
for(i=0;i<vecCad.length;i++)
cadRet += vecCad[i] + " ";
return cadRet;
}
//-----------------------
Talvez tengas problemas por la expresion regular, utilice una de validacion de correo electroni jajaja, solo le quite la '@'
Suerte