refoctror_list_using_map

```
main() {
  List<Test> first = [Test(1,"temp"), Test(2,"temp")];

  first.where((e)=> e.no==2).map((e){
    e.no= 5;
  }).toList();
  
first.forEach((e)=>
  print(e.toJson())
);
  
}

class Test{
 int no;
 final String  name; //here final plays important role, if variable final it can't be refatored
  
  Test( this.no, this.name);

  //only for print
  Object toJson() {
    return "${no} : $name";
  }
  
}
```