How to split the array values and store in a string in android?

I am getting the values from arraylist arr and storing those values in a string with comma separator. But for the last value also comma is adding. How can I remove that? Please help me...

My Code:

ArrayList<String> arr;  
 String str;
 
     for (int i = 0; i < arr.size(); i++) {
 
                 int kk = arr.size();
                 System.out.println("splitting test" + arr.get(i));
                 str += arr.get(i) + ",";
 
                 System.out.println("result" + str);
 
 
             }
 

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