Java8 十大新特性

1、lambda表达式

1）对象 =（变量…） ->{
方法实现
}
2）实例：

public class LambdaDemo{    public static void main(String[] args){        System.out.println("kk");        Runnable r =()->{            int i = 0;            System.out.println("i="+(i++));        };        Action action = (String content)->{            System.out.println(content);        };        action.execute("haha");    }    static  interface  Action{        void execute(String content);    }}

2、Stream泛型接口，有过滤功能

1）创建一个元素Person集合：people使用Stream 和 forEach显示该集合所以元素

public class Person {    public static enum Sex {        FEMALE, MALE;    }    public String name;    public int age;    public Sex sex;    public Person(String name, int age, Sex sex) {        this.name = name;        this.age = age;        this.sex = sex;    }    @Override    public String toString() {        return "Person{" +                "name='" + name + '\'' +                ", age=" + age +                ", sex=" + sex +                '}';    }}

打印所有信息

public class StreamDemo {    public static void main(String[] args){        List<Person> persons = initPersons();        Stream<Person> stream = persons.stream();        stream.filter(p -> p.sex == Person.Sex.FEMALE);        stream.forEach(                p -> System.out.println(p.toString())        );    }    public static List<Person> initPersons(){        List<Person> persons = new ArrayList<Person>();        Person person = new Person("tom", 22 , Person.Sex.FEMALE);        persons.add(person);        person = new Person("jack", 23 , Person.Sex.FEMALE);        persons.add(person);        person = new Person("lily", 24 , Person.Sex.FEMALE);        persons.add(person);        person = new Person("stone", 25 , Person.Sex.FEMALE);        persons.add(person);        return  persons;    }}

3、Stream求平均值

public class StreamDemo {    public static void main(String[] args) {        List<Person> persons = initPersons();        Stream<Person> stream = persons.stream();        double avgAge = stream.filter(p -> p.age > 18)        .filter(p -> p.name.indexOf("tom")>=0)        .mapToDouble(p -> p.age)        .average()        .getAsDouble();        System.out.println(avgAge);         }    public static List<Person> initPersons() {        List<Person> persons = new ArrayList<Person>();        Person person = new Person("tom", 22, Person.Sex.FEMALE);        persons.add(person);        person = new Person("jack", 23, Person.Sex.FEMALE);        persons.add(person);        person = new Person("lily", 24, Person.Sex.FEMALE);        persons.add(person);        person = new Person("stone", 25, Person.Sex.FEMALE);        persons.add(person);        return persons;    }}

4、LocateDate 与 LocateTime的用法

1)LocateDate.now():系统日期
2)LocateDate.of(int year, int month, int dayOfMonth):按指定日期创建LocateDate
3)getYear():返回日期中的年份
4)getMonth():返回日期中的月份
5)getDayOfMonth():返回月份中的日

public class LocateDateDemo {    public static void main(String[] args) {        LocalDate date = LocalDate.now();        System.out.println(date.toString());        System.out.println(date.getYear() + "年");        System.out.println(date.getMonth()+ "月");        System.out.println(date.getDayOfMonth() + "日");        LocalTime time = LocalTime.now();        System.out.println(time.getHour());        System.out.println(time.getMinute());        System.out.println(time.getSecond());        System.out.println(time.toString());        LocalDateTime dateTime = LocalDateTime.now();        System.out.println(dateTime.toString());        System.out.println(dateTime.getYear() + "年");        System.out.println(dateTime.getMonth()+ "月");        System.out.println(dateTime.getDayOfMonth() + "日");         System.out.println(dateTime.getHour());        System.out.println(dateTime.getMinute());        System.out.println(dateTime.getSecond());    }}

5、DateTimeFormatter

public class DateFormatterDemo {    public static void main(String[] args) {        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd:HH:mm:ss");        LocalDateTime dateTime = LocalDateTime.parse("2018-11-31:11:12:13",dtf);        System.out.println(dateTime.toString());    }}

6、ZonedDateTime系统时间

LocalDateTime dateTime = LocalDateTime.parse("2018-11-31:11:12:13",dtf);ZonedDateTime dt = ZonedDateTime.now();String formatDate = dt.format(dtf);System.out.println(formatDate);