jdk1.8 flatMap使用

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用法:Stream.of(T... values).flatMap(Function<? super T, ? extends Stream<? extends R>> mapper)

  1. 基本数据类型
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * @author by miao
 * @date 2020/10/22 19:27
 */
public class FlatMapDemo {

    public static void main(String[] args) {

        List<Integer> list1 = new ArrayList<>();
        List<Integer> list2 = new ArrayList<>();


        list1.add(1);
        list1.add(2);
        list1.add(3);
        list1.add(4);

        list2.add(5);
        list2.add(6);
        list2.add(7);

        List<Integer> result = Stream.of(list1, list2).flatMap(Collection::stream).collect(Collectors.toList());

        System.out.println(result);

    }

}

  1. 引用类型
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * @author by miao
 * @date 2020/10/22 19:27
 */
public class FlatMapDemo {

    public static void main(String[] args) {

        List<Student> students1 = new ArrayList<>();
        List<Student> students2 = new ArrayList<>();

        students1.add(new Student("小红", 15));
        students1.add(new Student("小绿", 19));

        students2.add(new Student("小紫", 26));


        List<Student> result = Stream.of(students1, students2).flatMap(Collection::stream).collect(Collectors.toList());
        System.out.println(result);

    }

}


class Student {

    private String name;

    private Integer age;

    public Student(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

结果

[Student{name='小红', age=15}, Student{name='小绿', age=19}, Student{name='小紫', age=26}]