博客

package Stream;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.IntSummaryStatistics;
import java.util.List;
import java.util.Optional;
import java.util.OptionalInt;
import java.util.stream.Collectors;

public class Java8Stream {
    public static void main(String[] args) {
        System.out.println("hello Stream");
        List<Person> list=getPersoms();

        //调用Stream(流)API函数
        //List<Person> studentList
        boolean isAllMatch=list.stream().allMatch(Person::isStudent);
        boolean isAnyMatch=list.stream().anyMatch(Person::isStudent);
        boolean isALLNotMatch=list.stream().noneMatch(Person::isStudent);
        System.out.println("is All student? "+isAllMatch);
        System.out.println("is Any student? "+isAnyMatch);
        System.out.println("is no student? "+isALLNotMatch);

        List<String> studentList=list.stream().
                filter(Person::isStudent).//筛选出学生
                //map((Person person)->person.getName()).//获取学生名字形成新的流
                map(Person::getName).
                collect(Collectors.toList());//将新的流返回给studentList
        System.out.println("studentList: "+studentList);


        //flatMap
        List<String> strlist=new ArrayList<String>();
        strlist.add("I am a boy");
        strlist.add("I love the girl");
        strlist.add("But the girl loves another girl");

        List<String> resultlist=strlist.stream().
                map(line->line.split(" ")).//转化为String[]
                flatMap(Arrays::stream).//转化为Stream
                distinct().//去除重复的String
                collect(Collectors.toList());//返回集合
        System.out.println("resultlist: "+resultlist);

        //获取第一个元素findFirst
        Optional<Person> person = list.stream().findFirst();
        System.out.println("findFirst: "+person.get());

        OptionalInt maxAge  =list.stream().mapToInt(Person::getAge).max();
        System.out.println("maxAge: "+maxAge.getAsInt());

        IntSummaryStatistics all=list.stream().collect(Collectors.summarizingInt(Person::getAge));

        System.out.println("sumAge:"+all.getSum()+"   aver"+all.getAverage()
                            +"   minAge"+all.getMin()+"   maxAge"+all.getMax());
    }




    /**
     * 测试数据 
     * @return
     */
    public static List<Person> getPersoms(){
        List<Person> list=new ArrayList<Person>();
        Person person;
        for(int i=0;i<10;i++){
            person=new Person();
            person.setAge(i);
            person.setName("lice"+String.valueOf(i));
            person.setStudent(true);
            list.add(person);
        }
        return list;
    }



    /**
     * 测试数据 
     * @return
     */
    public static List<Integer> getNumbers(){
        List<Integer> list=new ArrayList<Integer>();
        for(int i=0;i<10;i++)
            list.add(i);
        return list;
    }
}