1. 传统的日期格式器方法(线程不安全)
@Test
public void test() throws Exception{
//传统时间格式器(线程不安全)
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
//任务
Callable<Date> task = () -> sdf.parse("20201001");
//线程池
ExecutorService pool = Executors.newFixedThreadPool(10);
//模拟多线程
List<Future<Date>> futureList = new ArrayList<>();
for (int i = 0; i < 10; i++) {
futureList.add(pool.submit(task));
}
//输出结果
for (Future<Date> dateFuture : futureList) {
System.out.println(dateFuture.get());
}
}
//抛出了java.util.concurrent.ExecutionException: java.lang.NumberFormatException: multiple points
2. 传统的日期格式器解决线程安全方法(ThreadLocal)
//1.创建工具类，内部方法由绑定ThreadLocal的SimpleDateFormat提供。
public class SimpleDateFormatThreadLocal {
//创建一个ThreadLocal对象,并初始值为SimpleDateFormat对象
public static final ThreadLocal<SimpleDateFormat> sdf = new ThreadLocal<SimpleDateFormat>(){
protected SimpleDateFormat initialValue() {
return new SimpleDateFormat("yyyyMMdd");
}
};
//提供一个dateStr转换Date方法
public static Date convert(String dateStr) throws ParseException {
return sdf.get().parse(dateStr);
}
}
//2.测试(线程安全问题解读了)
@Test
public void test1() throws Exception{
//任务(使用绑定在ThreadLocal上的SimpleDateFormat对象转换)
Callable<Date> task = () -> SimpleDateFormatThreadLocal.convert("20201020");
//线程池
ExecutorService pool = Executors.newFixedThreadPool(10);
//模拟多线程
List<Future<Date>> futureList = new ArrayList<>();
for (int i = 0; i < 10; i++) {
futureList.add(pool.submit(task));
}
//输出结果
for (Future<Date> dateFuture : futureList) {
System.out.println(dateFuture.get());
}
//关闭线程池
pool.shutdown();
}
3. LocalDate新日期类(线程安全)
@Test
public void test2() throws Exception{
//新日期格式器(线程安全)
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyyMMdd");
//任务(LocalDate.parse(dateStr,dateTimeFormatter))
Callable<LocalDate> task = () -> LocalDate.parse("20201020",dtf);
//线程池
ExecutorService pool = Executors.newFixedThreadPool(10);
//模拟多线程
List<Future<LocalDate>> futureList = new ArrayList<>();
for (int i = 0; i < 10; i++) {
futureList.add(pool.submit(task));
}
//输出结果
for (Future<LocalDate> dateFuture : futureList) {
System.out.println(dateFuture.get());
}
//关闭线程池
pool.shutdown();
}
4. 新日期类、时间戳、时间间隔对象，日期间隔对象
//1.LocalDate LocalTime LocalDateTime 新日期类，类实例是不可变对象
@Test
public void test3(){
//获取当前日期对象
LocalDateTime ldt1 = LocalDateTime.now();
System.out.println(ldt1);
//获取指定日期对象
LocalDateTime ldt2 = LocalDateTime.of(2018, 10, 10, 11, 11, 11);
System.out.println(ldt2);
//日期对象运算
LocalDateTime ldt3 = ldt2.plusYears(1);
System.out.println(ldt3);
LocalDateTime ldt4 = ldt3.minusMonths(5);
System.out.println(ldt4);
//获取日期属性...
System.out.println("ldt4.getMonthValue() = " + ldt4.getMonthValue());
System.out.println("ldt4.getHour() = " + ldt4.getHour());
}
//2. Instant : 时间戳（使用 Unix 元年 1970年1月1日 00:00:00 所经历的毫秒值）
@Test
public void test4(){
//获取当前时间戳对象
Instant instant = Instant.now(); //默认UTC时区
System.out.println(instant);
//偏移量时间对象
OffsetDateTime offsetDateTime = instant.atOffset(ZoneOffset.ofHours(8)); //+8H 北京时间
System.out.println(offsetDateTime);
//获取指定时间戳对象
Instant instant1 = Instant.ofEpochSecond(60); //从Unix元年算起的时间戳
System.out.println(instant1); //1970-01-01T00:01:00Z
}
//Duration : 用于计算两个“时间”间隔
//Period : 用于计算两个“日期”间隔
@Test
public void test5() throws InterruptedException {
//时间间隔对象 Duration
Instant t1 = Instant.now();
Thread.sleep(1000);
Instant t2 = Instant.now();
Duration duration = Duration.between(t1, t2);
System.out.println(duration.toMillis());
//日期间隔对象 Period
LocalDate d1 = LocalDate.of(2020, 1, 1);
LocalDate d2 = LocalDate.now();
Period period = Period.between(d1, d2);
System.out.println(period.getYears()); //相差年数
System.out.println(period.getMonths()); //相差月数
System.out.println(period.getDays()); //相差天数
}
5.时间调整器 TemporaAdjuster
@Test
public void test6(){
//获取当前时间对象
LocalDateTime localDateTime = LocalDateTime.now();
System.out.println(localDateTime);
//指定月份为2
LocalDateTime localDateTime1 = localDateTime.withMonth(2);
System.out.println(localDateTime1);
//时间调整器工具类TemporalAdjusters.next指定下个周日
LocalDateTime localDateTime2 = localDateTime.with(TemporalAdjusters.next(DayOfWeek.SUNDAY));
System.out.println("next Sunday: " + localDateTime2);
//计算下个工作日(自定义时间调整器)
LocalDateTime localDateTime4 = localDateTime.with(temporal -> {
//强转日期类
LocalDateTime localDateTime3 = (LocalDateTime) temporal;
//获取周几
DayOfWeek dayOfWeek = localDateTime3.getDayOfWeek();
//返回下个工作日
if(dayOfWeek.equals(DayOfWeek.FRIDAY)){
return localDateTime3.plusDays(3);
}else if(dayOfWeek.equals(DayOfWeek.SATURDAY)){
return localDateTime3.plusDays(2);
}else {
return localDateTime3.plusDays(1);
}
});
System.out.println("next workDay: " + localDateTime4);
}
6.时间格式器 DateTimeFormatter
@Test
public void test7(){
//日期格式器
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy年MM月dd日 HH:mm:ss");
//当前时间对象
LocalDateTime now = LocalDateTime.now();
//格式化当前日期 localDateTime => dateStr
String dateStr = dateTimeFormatter.format(now);
System.out.println(dateStr);
//解析日期字符串 dateStr => localDateTime
LocalDateTime lacalDateTime = LocalDateTime.parse(dateStr, dateTimeFormatter);
System.out.println(lacalDateTime);
}
7.ZonedDate、ZonedTime、ZonedDateTime ： 带时区的时间或日期
@Test
public void test8(){
//获取所有时区字符串表现形式
Set<String> set = ZoneId.getAvailableZoneIds();
//set.forEach(System.out::println);
//设置为亚洲/东京时区时间
LocalDateTime localDateTime = LocalDateTime.now(ZoneId.of("Asia/Tokyo"));
System.out.println(localDateTime);
//为日期对象添加时区信息
ZonedDateTime zonedDateTime = localDateTime.atZone(ZoneId.of("Asia/Tokyo"));
System.out.println(zonedDateTime);
}
8.可重复注解
//1. Annotation注解容器
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotations {
MyAnnotation[] value();
}
//2. Annotation注解 -> @Repeatable(MyAnnotations.class) 指定注解容器
@Repeatable(MyAnnotations.class)
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
String value() default "codeDuck";
}
//3. 使用和测试
public class TestAnno {
//重复注解
@MyAnnotation("hello")
@MyAnnotation("world")
public void demo(){}
@Test
public void test() throws NoSuchMethodException {
//字节码对象
Class<TestAnno> testAnnoClass = TestAnno.class;
//获取demo方法对象
Method demo = testAnnoClass.getMethod("demo");
//获取MyAnnotation.class类型注解对象
MyAnnotation[] annotations = demo.getAnnotationsByType(MyAnnotation.class);
for (MyAnnotation annotation : annotations) {
System.out.println(annotation.value()); // hello \n world
}
}
}
