Concatenating Mulitple fields into single string

Hi Experts;

I am trying to Concate multiple fields at which are on source side and send into one string at target side.

Source

<Header>Occurance 1

F1

F2

F3(Hard Coded =A)

<Header/>

<item>Occurance 0 to N

F4

F5

F6(Hard Coded =B)

F7

F8

F9(Hard Coded =C)

F10

F11

F12

F13

<item/>

Target

<Data>

I am using the below code however it's not working

String finalString = "";

int count = streng.length;   //  input string array count

for(int i=0;i<count;i++)

{

     finalString = finalString + streng<i>;

}

result.addValue(finalString);

can anyone suggest on this.

Regards