• arrayList is converted into the comma separated string.
• For this take one by one element from the arrayList.
• Then add it to the String array.

import java.util.ArrayList;

public class List1 {
    public static void main(String[] args) {
     int ar[]={1,2,3,4};
     ArrayList list=new ArrayList();
     list.add(ar[0]);
     list.add(ar[1]);
     list.add(ar[2]);
     list.add(ar[3]);

     String a=new String();

     for(int p:ar)
     {
      Integer x=new Integer(p);
      a=a+new Integer(p).toString()+",";
     }
     System.out.println(a);
  }
}
Output
1,2,3,4

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