How to get the first element of the List or Set?

To get the first element of a List or Set in Java, you can use the following methods:

  1. List:
List<String> list = new ArrayList<>();
// add elements to the list
String first = list.get(0);

Note that this will throw an IndexOutOfBoundsException if the list is empty.

  1. Set:
Set<String> set = new HashSet<>();
// add elements to the set
String first = set.iterator().next();

Note that this will throw a NoSuchElementException if the set is empty.

Alternatively, you can use the stream() method to get the first element of a List or Set in a more concise way:

List<String> list = new ArrayList<>();
// add elements to the list
String first = list.stream().findFirst().orElse(null);

Set<String> set = new HashSet<>();
// add elements to the set
String first = set.stream().findFirst().orElse(null);

This will return an Optional<T> object containing the first element of the List or Set, or an empty optional if the list or set is empty. You can then use the orElse() method to specify a default value to be returned if the optional is empty.