Combining random characters to make a string Java -

i trying make program combines group of characters randomly grabbed pool string called name. problem have makes 1 letter, when ends printing 1 letter, when should more.

  //determining first name   for(int g = 0; g < name_length_first; g++) {     char randomchar = pool[random.nextint((pool.length) - 1) + 1];     person_name_first = new stringbuilder().append(randomchar).tostring();   } 

how recommend go fixing this?

stringbuilder partialname = new stringbuilder();  for(int g = 0; g < name_length_first; g++) {     char randomchar = pool[random.nextint((pool.length) - 1) + 1];     partialname.append(randomchar); }  person_name_first = partialname.tostring();