import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.time.LocalDate;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class Test7 {
public static void main(String[] args) {
List<User> list = new ArrayList<>();
User user14 = new User();
user14.setName("小红1");
user14.setAge(14);
list.add(user14);
User user1 = new User();
user1.setName("小明");
user1.setAge(1);
list.add(user1);
User user2 = new User();
user2.setName("小明");
user2.setAge(2);
list.add(user2);
User user3 = new User();
user3.setName("小明");
user3.setAge(3);
list.add(user3);
User user4 = new User();
user4.setName("小明");
user4.setAge(4);
list.add(user4);
User user11 = new User();
user11.setName("小红");
user11.setAge(11);
list.add(user11);
User user12 = new User();
user12.setName("小明");
user12.setAge(1);
list.add(user12);
User user13 = new User();
user13.setName("小红");
user13.setAge(13);
list.add(user13);
Map<String, Long> map = list.stream().collect(Collectors.groupingBy(User::getName, Collectors.counting()));
map.forEach((k, v) -> {
System.out.println("k --> " + k + ", v --->" + v);
});
String s = map.entrySet().stream().map(e -> e.getKey() + " * " + e.getValue()).sorted().collect(Collectors.joining(","));
System.out.println(s);
}
}
class User {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
结果
k --> 小明, v --->5
k --> 小红1, v --->1
k --> 小红, v --->2
小明 * 5,小红 * 2,小红1 * 1
