阅读量:0
本文主要用于记录jdk8以来的新增特性及使用方法!
1.Java8 Lambda表达式(8)
1.1 方法引用
List<String> list = List.of("1", "2", "3"); list.forEach(i -> System.out.println(i)); //方法引用 list.forEach(System.out::println); 1.2 接口支持默认方法
public interface MyTest { default void defaultMethod(){ System.out.println("default Method"); } } 1.3 Stream API流式API
List<String> list = List.of("1", "2", "3"); //过滤再循环 list.stream().filter(i -> !"1".equals(i)).forEach(System.out::println); //过滤再输出 List<String> list1 = list.stream().filter(i -> !"1".equals(i)).toList(); System.out.println(JSONObject.toJSONString(list1)); //["2","3"] //过滤再转map List<Map<String, Object>> list2 = list.stream().filter(i -> !"1".equals(i)).map(s -> { Map<String, Object> map = new HashMap<>(); map.put("a_" + s, s); return map; }).toList(); System.out.println(JSONObject.toJSONString(list2)); //[{"a_2":"2"},{"a_3":"3"}] //转类型 List<Long> list3 = list.stream().map(Long::valueOf).toList(); System.out.println(JSONObject.toJSONString(list3)); //[1,2,3] 1.4 Map新增且实用的方法
Map<String, Integer> map = new HashMap<>(); map.put("a", 1); map.put("b", 2); //foreach map.forEach((key, value) -> System.out.println(key + ": " + value)); //getOrDefault 取值为空返回默认值 int c = map.getOrDefault("c", 22); System.out.println(c); //22 //replace 如果存在值替换当前key的值 map.replace("b", 10); System.out.println(map); //{a=1, b=10} //替换时带匹配值 map.replace("b", 10, 20); System.out.println(map); //{a=1, b=20} //replaceAll 可对每个key或者value做操作 map.replaceAll((key, value) -> value + 1); System.out.println(map); //{a=2, b=21} //putIfAbsent key不存在才存入 map.putIfAbsent("a", 11); map.putIfAbsent("c", 3); System.out.println(map); //{a=2, b=21, c=3} //computeIfAbsent 如果值不存在 则执行后面的函数 map.computeIfAbsent("d", key -> 4); System.out.println(map); //{a=2, b=21, c=3, d=4} //computeIfPresent 如果存在且值非空 可重新计算 map.computeIfPresent("b", (key, value) -> value + 10); System.out.println(map); //{a=2, b=31, c=3, d=4} //compute 使用函数计算存入 map.compute("b", (key, value) -> (value == null) ? 40 : value + 1); map.compute("e", (key, value) -> (value == null) ? 40 : value + 1); System.out.println(map); //{a=2, b=32, c=3, d=4, e=40} //merge map.merge("b", 1, (oldValue, newValue) -> oldValue + newValue); System.out.println(map); //{a=2, b=33, c=3, d=4, e=40} //remove 当指定key和值时才删除 map.remove("a", 1); System.out.println(map); //{a=2, b=33, c=3, d=4, e=40} map.remove("a", 2); System.out.println(map); //{b=33, c=3, d=4, e=40} //of ofEntries 快捷创建 但映射不可变 Map<String, Integer> of = Map.of("a", 1, "b", 2); System.out.println(of); //{b=2, a=1} Map<String, Integer> ofEntries = Map.ofEntries( Map.entry("a",1), Map.entry("b",2) ); System.out.println(ofEntries); //{b=2, a=1} // of.put("a",3); //不管新增删除还是修改 俊辉报错 2. java11 var httpClient相关(11)
var list = List.of("1", "2", "3"); list.forEach((var e) -> System.out.println(e)); String str = " "; System.out.println(str.isBlank()); //true System.out.println(str.isEmpty()); //false //java.net.http JSONObject object = new JSONObject(); object.put("fromId", 11234); var httpClient = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(6)).build(); HttpRequest httpRequest = HttpRequest.newBuilder(URI.create("http://192.168.168.199:9000/xxxxxx")) //post body请求 // .setHeader("Content-Type","application/json; charset=utf-8") // .POST(HttpRequest.BodyPublishers.ofString(object.toJSONString())) .build(); HttpResponse<String> httpResponse = httpClient.send(httpRequest, HttpResponse.BodyHandlers.ofString()); System.out.println(httpResponse.body()); //okhttp3 http请求 // Request request = new Request.Builder() // .url(noticeUrl) .get() // .post(RequestBody.create(object.toJSONString(), MediaType.parse("application/json; charset=utf-8"))) // .build(); // Response response = Web3jUtils.httpClient.newCall(request).execute(); // JSONObject jsonObject = JSONObject.parseObject(response.body().string()); // log.warn("发现提现消息:{},{}", object.toJSONString(), jsonObject.toJSONString()); 3.新表达式和模块匹配(12-15)
3.1 switch 多行文本 instanceof
int day = 1; switch (day){ case 2 -> System.out.println(false); case 1 -> System.out.println(true); default -> System.out.println("未知的!"); } //多行文本 String str = """ text text """; //instanceof if(str instanceof String s1){ System.out.println(s1.toUpperCase(Locale.ROOT)); } 4.记录 密封类 虚拟线程(16-21)
- 记录
public record Point(int x, int y) {} - 密封类
public abstract sealed class Shape permits Circle, Square {} public final class Circle extends Shape {} public final class Square extends Shape {} - 虚拟线程
Thread.ofVirtual().start(() -> { System.out.println("Hello from virtual thread"); }); //使用Executors 创建和管理 ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor(); for (int i = 0; i < 10; i++) { executor.submit(() -> { System.out.println("Hello from virtual thread!"); }); } executor.shutdown(); 以上就是本文的全部内容了！
上一篇：随手记录第十一话 – PHP + yii2 初体验
下一篇：随手记录第十三话 – 关于Python自动化部署神器fabric的应用与差异
非学无以广才，非志无以成学。
