java list get first element

final Object firstElement = list.stream()
  .findFirst()
  .orElse(new Object()) //Give a default value if there are no elements
  
final Object firstElement = list.stream()
  .findFirst()
  .orElseThrow(() -> new Exception()) //Throw an exception if there are no elements  

list.get(0);

set.iterator().next();

!list_or_set.isEmpty()