The supplier allows you to pass something but not retrieve it right away. One use case is retrieving a property an object that could throw a null pointer exception. By not retrieving right away, but instead using a supplier, the supplier can be later executed inside a try/catch block and handle any exceptions thrown.
An incredible tool in Java is the ability to create functions and compose them.
public static LocalDate parseDate(String date) {
DateTimeFormatter formatter =
DateTimeFormatter.ofPattern("M/d/y");
return LocalDate.parse(date,formatter);
}
@Test
public void testDateParsing() {
String testDate;
testDate ="01/01/2022";
LocalDate expected = LocalDate.of(2022, 1, 1);
assertEquals(expected, DateParser.parseDate(testDate));
}
@Test
public void testDateParsingSingleDigitMonthAndYear() {
String testDate;
testDate = "1/1/2022";
LocalDate expected = LocalDate.of(2022, 1, 1);
assertEquals(expected, DateParser.parseDate(testDate));
}
for(String name: names) {
System.out.println(name);
}
// This is called a method reference
names.foreach(System.out::println);
Often we have to loop through a list of items and convert it into a map, with the key being some sort of category and the value being a set of the associated items ie Map<Key, Set<Object>>. The old way of doing this looped through the list and before adding checked if the key was present. Using computeIfAbsent we can clean up this syntax considerably.
