Java 8速查表
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1 2 3 | (parameters) -> expression(parameters) -> statement(parameters) -> { statements } |
1 2 3 | (int x, int y) -> x + y() -> System.out.println("hi " + s);(String s) -> { int n = s.length(); return n; } |
1 2 | Runnable r = () -> System.out.println("Hello!");r.run(); |
1 2 | Callable<Double> pi = () -> 3.14;Double p = pi.call(); |
1 2 3 4 5 | String[] words = {"aaa", "b", "cc"};Arrays.sort(words, (s1, s2) -> s1.length() - s2.length());// 等價(jià)于：Arrays.sort(words, (String s1, String s2) -> s1.length() - s2.length()); |
1 2 3 4 5 | // s是高效的final變量（不會更改）String s = "foo";// s可以在lambdas中被引用Runnable r = () -> System.out.println(s); |
1 2 3 4 5 | // Class::staticMethod syntaxArrays.sort(items, Util::compareItems);// 等價(jià)于:Arrays.sort(items, (a, b) -> Util.compareItems(a, b)); |
1 2 3 4 5 | // instance::instanceMethod syntaxitems.forEach(System.out::print);// 等價(jià)于：items.forEach((x) -> System.out.print(x)); |
1 2 3 4 5 | // Class::instanceMethod syntaxitems.forEach(Item::publish);// 等價(jià)于:items.forEach((x) -> { x.publish(); }); |
1 2 | ConstructorReference cref = Item::new;Item item = cref.constructor(); |
1 2 3 4 5 6 7 | interface Descriptive { default String desc() { return "fantastic"; }} |
1 2 3 4 5 6 | class Item implements Descriptive { }Item x = new Item();// prints "fantastic"System.out.println(x.desc()); |
1 2 | List<String> strings = ...;long n = strings.stream().filter(x -> !x.isEmpty()).count(); |
1 2 | List<Item> items = ...;String names = items.stream().map((x) -> x.getTitle()).collect(Collectors.joining(", ")); |
1 2 | List<City> cities = ...;List<Country> countries = cities.stream().map((c) -> c.getCountry()).distinct().collect(Collectors.toList()); |
1 2 | List<Item> items = ...;IntSummaryStatistics stats = items.stream().mapToInt((x) -> x.getRating()).summaryStatistics(); |
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