Well, apparently I had to change my PUT calling function updateUser. I removed the @Consumes, the @RequestMapping and also added a @ResponseBody to the function. So my method looked like this:
@RequestMapping(value="/{id}",method = RequestMethod.PUT)
@ResponseStatus(HttpStatus.OK)
@ResponseBody
public void updateUser(@PathVariable int id, @RequestBody User temp){
Set<User> set1= obj2.getUsers();
for(User a:set1)
{
if(id==a.getId())
{
set1.remove(a);
a.setId(temp.getId());
a.setName(temp.getName());
set1.add(a);
}
}
Userlist obj3=new Userlist(set1);
obj2=obj3;
}
And it worked!!! Thank you all for the response.