Технологии Java
Лямбда-выражения и потоки
BiFunction<String, Long, String> f =
(String s, Long v) −> {
return s + v;
}
BiFunction<String, Long, String> f =
(String s, Long v) −> s + v;
BiFunction<String, Long, String> f = (s, v) −> s + v;
Function<String, String> f = s −> s + s;
Supplier<String> s = () −> "!";
Consumer<String> c = s −> System.out.println(s + s);
default <V> Function<V, R>
compose(Function<−V, +T> before) {
return v −> apply(before.apply(v));
}
default <V> Function<T, V>
andThen(Function<−R, +V> after) {
return v −> after.apply(apply(v));
}
Function<String, Integer> f1 = Integer::parseInt; // x −> Integer.parseInt(x);
Function<Integer, String> f2 = Integer::toString; // x −> x.toString();
Integer i = 2; // Не обязательно final Supplier<String> f3 = i::toString; // () −> i.toString();
Function<String, Integer> f = Integer::new; // s −> new Integer(s);
/* final */ String hello = "Hello, ";
Function<String, String> greeter =
name −> hello + name;
// Не работает, так как write бросает IOException Consumer<String> c = writer::write;
collection.forEach(e −> {
if (e.equals("done")) {
// Что делать?
}
});
@FunctionalInterface
interface IOSupplier<T> {
T get() throws IOException;
static <T> T unchecked(IOSupplier<T> supplier) {
try {
return supplier.get();
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
}
List<String> lines = IOSupplier.unchecked(() −>
Files.readAllLines(Path.of("input.txt")));
courses.sort(
Comparator.comparingInt(Course::getYear)
.thenComparingInt(Course::getTerm)
.thenComparing(
Course::getName,
String.CASE_INSENSITIVE_ORDER
))
courses.forEach(System.out::println);
courses.removeIf(Course::isDone);
courses.toArray(Course[]::new);
courses.replaceAll(Course::nextYear);
Map<String, Integer> map = new HashMap<>();
while (scanner.hasNext()) {
map.merge(scanner.next(), 1, Integer::sum);
}
Map<String, Integer> map = new HashMap<>();
Files.readAllLines(input).forEach(line −> {
for (String word : line.split("\\s+")) {
map.merge(word, 1, Integer::sum);
}
});
string.stream()
.filter(s −> s.endsWith("s"))
.mapToInt(String::length)
.min();
string.parallelStream()
.filter(s −> s.contains("a"))
.sorted(String.CASE_INSENSITIVE_ORDER)
.limit(3)
.collect(Collectors.joining(", "));
Map<String, Long> map = words.stream()
.collect(Collectors.groupingBy(
String::toUpperCase,
Collectors.counting()
));
Map<String, Long> map = Files.lines(path)
.flatMap(line −> Arrays.stream(line.split("\\s+"))
.collect(Collectors.groupingBy(
String::toUpperCase,
Collectors.counting()
));
words.stream()
.collect(Collectors.joining(", ", "{", "}"));
Collector<Student, String[], Map.Entry<String, String>>
MIN_NAMES = Collector.of(
() −> new String[2],
(mins, Student) −> {
mins[0] = min(mins[0], Student.getFirstName());
mins[1] = min(mins[1], Student.getLastName());
},
(mins1, mins2) −> {
mins1[0] = min(mins1[0], mins2[0]);
mins1[1] = min(mins1[1], mins2[1]);
return mins1;
},
mins −> Map.entry(mins[0], mins[1])
);