在Java中如何使用Collectors.summarizingInt汇总集合整数_Collectors汇总技巧

import java.util.stream.Collectors;
import java.util.IntSummaryStatistics;
import java.util.List;

class User {
    private String name;
    private int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public int getAge() {
        return age;
    }
}

List users = List.of(
    new User("Alice", 25),
    new User("Bob", 30),
    new User("Charlie", 35)
);

IntSummaryStatistics stats = users.stream()
    .collect(Collectors.summarizingInt(User::getAge));

System.out.println(stats);
// 输出：IntSummaryStatistics{count=3, sum=90, min=25, average=30.000000, max=35}

System.out.println("人数: " + stats.getCount());
System.out.println("总年龄: " + stats.getSum());
System.out.println("平均年龄: " + stats.getAverage());
System.out.println("最大年龄: " + stats.getMax());
System.out.println("最小年龄: " + stats.getMin());

List numbers = List.of(1, 3, 5, 7, 9);
IntSummaryStatistics numStats = numbers.stream()
    .collect(Collectors.summarizingInt(Integer::intValue));

System.out.println(numStats);
// 输出：IntSummaryStatistics{count=5, sum=25, min=1, average=5.000000, max=9}