Question

String query = "select email from emp_select";
Statement stmt;

try {

  DB db=new DB(); 
  db.connect();
  stmt = (Statement) db.conn.createStatement(); // DB is connected here              

  ResultSet rs = stmt.executeQuery(query);
  ResultSetMetaData rsmd = rs.getMetaData();

  int numberOfColumns = rsmd.getColumnCount();

  for (int i = 1; i <= numberOfColumns; i++) {
    if (i > 1)
        System.out.print(",  ");
  }
  System.out.println("");

  while (rs.next()) {
    for (int i = 1; i <= numberOfColumns; i++) {
        if (i > 1)
            System.out.print(",  ");

        String columnValue = rs.getString(i);
        name[i]=columnValue;
        System.out.println(name[i]);          //Everything executes well till here
    }
  }
  stmt.close();
} catch(Exception ex) {}

for (int i = 1; i < name.length; i++) {
    System.out.println(name[i]);   // why it gives null value here ?
}

Answer 1

I was wondering is this what you really want :

while (rs.next()) {
    for (int i = 1; i <= numberOfColumns; i++) {
        if (i > 1)
            System.out.print(",  ");

        String columnValue = rs.getString(i);
        name[i]=columnValue;
        System.out.println(name[i]);          //Everything executes well till here
    }
  }

Here what is happening is , the while loop starts, now for loop begins execution, now inside the for loop you are giving all elements of name array the same value i.e. rs.getString(i), but your query returns only one column for your rs, i.e. email (but you coding in your for loop something like names[2] = rs.getString(2), name[3] = rs.getString(3), but here there is nothing other than rs.getString(1)). Seems like what you should do is this, that might can give you expected results

for (int i = 1; i <= numberOfColumns; i++) {
        if (i > 1)
            System.out.print(",  ");
        if (rs.next()) // hope this works, not sure (but it does works for me at the click of a button, when used through Swing Events)
        {
            String columnValue = rs.getString(1);// Since only one thing is being returned by your rs object.
            name[i]=columnValue;
            System.out.println(name[i]);          //Everything executes well till here
        }
    }

Hopefully this might can solve.

Regards