HashMap
import java.util.*; public class MyApp{ public static void main(String[] args){ HashMap<String, Integer> sales = new HashMap<>(); sales.put("tom", 10); sales.put("john", 20); sales.put("mason", 30); System.out.println(sales.get("tom")); System.out.println(sales.size()); for (Map.Entry<String, Integer> sale: sales.entrySet()){ System.out.println(sale.getKey() + ":" + sale.getValue()); } } }
StreamAPI
import java.util.*; public class MyApp{ public static void main(String[] args){ List<Integer> sales = new ArrayList<>(Arrays.asList(12, 30, 22, 4, 9)); sales .stream() // 中間処理 .filter(e -> e % 3 == 0) // 終端処理 .map(e -> "(" + e+ ")") .forEach(System.out::println); } }
LocalDateTime
import java.time.*; import java.time.format.DateTimeFormatter; public class MyApp{ public static void main(String[] args){ LocalDateTime d = LocalDateTime.now(); // LocalDateTime d = LocalDateTime.of(2017, 1, 1, 10, 10, 10); // LocalDateTime d = LocalDateTime.parse("2016-12-12T10:10:10"); System.out.println(d.getYear()); System.out.println(d.getMonth()); System.out.println(d.getMonth().getValue()); System.out.println(d.plusMonths(2).minusDays(3)); DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy!MM!dd!"); System.out.println(d.format(dtf)); } }