import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class Demo1 {
public static void main(String[] args) {
User user1 = new User(1, "u1", "shenyang", "hahaha");
User user2 = new User(2, "u2", "shenyang", "gaga");
User user3 = new User(3, "u3", "shanghai", "lala");
User user4 = new User(4, "u4", "shanghai", "hahaha");
User user5 = new User(5, "u5", "shenyang", "gaga");
User user6 = new User(6, "u6", "shanghai", "hahaha");
User user7 = new User(7, "u7", "beijing", "gaga");
User user8 = new User(8, "u8", "beijing", "hahaha");
User user9 = new User(9, "u9", "shenyang", "lala");
Listlis = new ArrayList<>();
lis.add(user1);
lis.add(user2);
lis.add(user3);
lis.add(user4);
lis.add(user5);
lis.add(user6);
lis.add(user7);
lis.add(user8);
lis.add(user9);
//Listlis1 =lis.stream().filter(a->a.getAdd().equals("shenyang")).collect(Collectors.toList());
//lis1.forEach(a->System.out.println(UserOp.getInfo(a)));
int numcount =lis.stream().mapToInt(a->a.getNum()).sum();
System.out.println(numcount);
Listaa=lis.stream().map(a->UserOp.getname(a)).collect(Collectors.toList());
aa.forEach(a->System.out.println(a));
}
}
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class Demo3 {
public static void main(String[] args) {
User user1 = new User(1, "u1", "shenyang", "hahaha");
User user2 = new User(2, "u2", "shenyang", "gaga");
User user3 = new User(3, "u3", "shanghai", "lala");
User user4 = new User(4, "u4", "shanghai", "hahaha");
User user5 = new User(5, "u5", "shenyang", "gaga");
User user6 = new User(6, "u6", "shanghai", "hahaha");
User user7 = new User(7, "u7", "beijing", "gaga");
User user8 = new User(8, "u8", "beijing", "hahaha");
User user9 = new User(9, "u9", "shenyang", "lala");
Listlis = new ArrayList<>();
lis.add(user1);
lis.add(user2);
lis.add(user3);
lis.add(user4);
Listlis2 = new ArrayList<>();
lis2.add(user5);
lis2.add(user6);
lis2.add(user7);
lis2.add(user8);
lis2.add(user9);
Listfigures = Stream.of(lis, lis2).flatMap(u -> u.subList(0, 1).stream()).collect(Collectors.toList());
figures.forEach(f -> System.out.println(f.getName()));
}
}
通过以上示例代码，很容易发现其实map主要是用于遍历每个参数，然后进行参数合并或者返回新类型的集合。
FlatMap主要是用于stream合并，这个功能非常实用，他是默认实现多CPU并行执行的，所以我们合并集合优先实用这种方式。
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