java8 异步api、循环、日期
java8 异步api、循环、日期
转载请注明出处：https://cloud.tencent.com/developer/article/1456797
异步api
对于多任务耗时的业务场景，一般我们会用到线程异步处理,在以前我们用 Thread 或者 Runnable 来实现异步，这是oracle官方做法，不过缺点很明显
- 对于复杂业务场景需要配置线程池
- 代码繁杂，对于新手容易造成不必要的bug
- 如果涉及到线程锁或线程通讯就棘手了
现在，java8为我们提供了CompletableFuture类，可以完全解决以上问题。
主要方法有:
runAsync()异步无参返回- 样例:
@Test public void asyncThread()throws Exception{ CompletableFuture async1 = CompletableFuture.runAsync(()->{ try { Thread.sleep(1000); System.out.println(Thread.currentThread().getName()); System.out.println("none return Async"); }catch (Exception e){ e.printStackTrace(); } }); // 调用get()将等待异步逻辑处理完成 async1.get(); }
supplyAsync()异步有参返回- 样例:
@Test public void asyncThread2()throws Exception{ CompletableFuture<String> async2 = CompletableFuture.supplyAsync(()->{ return "hello"; }); String result = async2.get(); // String result2 = async2.get(5L, TimeUnit.SECONDS); System.out.println(result); }
allOf()多个异步处理(针对有参返回)- 样例：
@Test public void asyncThread3()throws Exception{ CompletableFuture<String> a = CompletableFuture.supplyAsync(() -> "hello"); CompletableFuture<String> b = CompletableFuture.supplyAsync(() -> "youth"); CompletableFuture<String> c = CompletableFuture.supplyAsync(() -> "!"); CompletableFuture all = CompletableFuture.allOf(a,b,c); all.get(); String result = Stream.of(a, b,c) .map(CompletableFuture::join) .collect(Collectors.joining(" ")); System.out.println(result); }
anyOf()多个异步随机处理(针对有参返回)- 样例
@Test public void asyncThread4()throws Exception{ CompletableFuture<String> a = CompletableFuture.supplyAsync(() ->{ try{ Thread.sleep(20); return "hello"; }catch (Exception e){ e.printStackTrace(); return "none~"; } }); CompletableFuture<String> b = CompletableFuture.supplyAsync(() -> "youth"); CompletableFuture<String> c = CompletableFuture.supplyAsync(() -> "!"); CompletableFuture<Object> any = CompletableFuture.anyOf(a,b,c); String result = (String)any.get(); System.out.println(result); }
循环ForEach
java8 在原有for或iterator循环下又提供了 forEach 的方法，不过与for循环不同的是 forEach 循环是建立在stream之上的,而且比for或iterator方便的是，他可以循环Map对象，
如果您尝试配合filter处理就更赞了~
- forEach对List的循环样例
@Test
public void listForeach(){
List<String> lst = new ArrayList<String>(5){{
add("A");
add("B");
add("H");
add("O");
add("M");
}};
lst.forEach(System.out::println);
lst.forEach((item)-> System.out.println(item.concat("_")));
}- forEach对数组的循环 样例
@Test
public void arrForeach(){
String[] strArr = new String[]{"A","B","C","D"};
Arrays.stream(strArr).forEach(System.out::println);
}- forEach对int范围的循环 样例
@Test
public void numericForeach(){
IntStream.range(0,10).forEach(System.out::println);
}- forEach对Map的循环 样例:
@Test
public void mapForeach(){
Map<String,Object> mps = new HashMap<String,Object>(5){{
put("a",1);
put("b",true);
put("c",23.44F);
put("d","hello");
put("e",11L);
}};
mps.forEach((k,v)-> System.out.println(k.concat(":").concat(String.valueOf(v))));
String str = "hello";
}新的时间类(LocalDate、LocalDateTime)
java8 之前我们处理时间 大多会涉及到这几个类Date、SimpleDateFormat、Calendar ，这种处理方式复杂、存在线程隐患、国际化困难、日期加减等处理麻烦等等。
现在有了 LocalDate、LocalDateTime、DateTimeFormatter 生活就变得简单了~
- 格式化及区域定义
/**设置格式化模板**/
private static final DateTimeFormatter DATE_TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSS");
/**设置日期时区常量**/
public static final ZoneId CHINA_ZONE_ID = ZoneId.systemDefault();- Date格式化为DateTime
/**Date格式化为DateTime**/
@Test
public void dateToDateTime(){
Date date = new Date();
LocalDateTime dateTime = date.toInstant().atZone(CHINA_ZONE_ID).toLocalDateTime();
System.out.println(dateTime);
}- LocalDate/LocalDateTime转Date
/**LocalDate/LocalDateTime转Date**/
@Test
public void toDate(){
// LocalDate
LocalDate localDate = LocalDate.now();
Date d1 = Date.from(localDate.atStartOfDay(CHINA_ZONE_ID).toInstant());
System.out.println(d1);
// LocalDateTime
LocalDateTime localDateTime = LocalDateTime.now();
Date d2 = Date.from(localDateTime.atZone(CHINA_ZONE_ID).toInstant());
System.out.println(d2);
}- 日期格式化
/**日期格式化**/
@Test
public void formatDate(){
System.out.println(LocalDateTime.now().format(DATE_TIME_FORMATTER));
}- 日期加减
/**日期加减**/
@Test
public void plusDay(){
LocalDateTime dateTime = LocalDateTime.now(CHINA_ZONE_ID);
//天
dateTime=dateTime.plusDays(1);
//时
dateTime=dateTime.plusHours(-1);
//分钟
dateTime=dateTime.plusMinutes(30);
System.out.println(dateTime.format(DATE_TIME_FORMATTER));
}- 日期时间间隔
/**日期时间间隔**/
@Test
public void betweenDay(){
// LocalDateTime
LocalDateTime startDate = LocalDateTime.of(2019,07,01,12,12,22);
LocalDateTime endDate = LocalDateTime.of(2019,07,03,12,12,22);
Long withSecond = endDate.atZone(CHINA_ZONE_ID).toEpochSecond() - startDate.atZone(CHINA_ZONE_ID).toEpochSecond();
System.out.println(withSecond/60/60/24);
// LocalDate
LocalDate startDate2 = LocalDate.of(2019,07,01);
LocalDate endDate2 = LocalDate.of(2019,07,03);
Long withSecond2 = endDate2.toEpochDay() - startDate2.toEpochDay();
System.out.println(withSecond2);
}- 第一天and最后一天
/**第一天and最后一天**/
@Test
public void theLastDay(){
// 当月第一天
LocalDateTime dateTime = LocalDateTime.of(2019,07,03,12,12,22);
dateTime = dateTime.with(TemporalAdjusters.firstDayOfMonth());
System.out.println(dateTime);
// 当月最后一天
dateTime = dateTime.with(TemporalAdjusters.lastDayOfMonth());
System.out.println(dateTime);
//当月的第几天
dateTime = LocalDateTime.now();
int dayOfMonth = dateTime.getDayOfMonth();
System.out.println(dayOfMonth);
// 当前周的第几天
int dayOfWeek = dateTime.getDayOfWeek().getValue();
System.out.println(dayOfWeek);
}OK，本次分享就到这里，如有谬误恳请指正~
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