It is common problem of convertion between int & string for certian computer language. Well, in Java, following are some easy ways I usually apply:

1. int --> String
    a. apply "+" operation with an empty string
          ex:
          int index = 20;
          String indexStr = "" + index;
    b. use String function
          ex:
          int index = 20;
          String indexStr = String.valueOf(index);
    c. convert to Integer class firstly
          ex:
          int index = 20;
          Integer Index = new Integer(index);
          String indexStr = Index.toString();
          or
          String indexStr = Integer.toString(index);

2. String --> int
    a. use class Integer parse funtion
       ex:
       String indexStr = "20";
       int index = Integer.parseInt(indexStr);
       or
       int index = (new Integer(indexStr)).intValue();

note: above convertion methods can be applied to other number types, such as float, long, double...

P.S. for 1.a method, should be noticed that following two expression are different:
int i = 7;
int j = 8;

String str1 = i + j + ""; //(str1 == "15")
String str2 = "" + i + j; //(str2 == "78")