public class ListTest03 {
@Test
public void test() {
List<Student> list = new ArrayList<>();
Student s1 = new Student();
s1.setId(1);
s1.setName("张三");
s1.setAge(28);
Student s2 = new Student();
s2.setId(2);
s2.setName("李四");
s2.setAge(29);
Student s3 = new Student();
s3.setId(3);
s3.setName("网二");
s3.setAge(30);
list.add(s1);
list.add(s2);
list.add(s3);
System.out.println(list);
//[Student(id=1, name=张三, age=28), Student(id=2, name=李四, age=29), Student(id=3, name=网二, age=30)]
System.out.println("=========第一种方式================");
int suma = list.stream().map(e -> e.getAge()).reduce(Integer::sum).get();//求和 87
System.out.println(suma);
int maxa = list.stream().map(e -> e.getAge()).reduce(Integer::max).get();//最大 30
System.out.println(maxa);
int mina = list.stream().map(e -> e.getAge()).reduce(Integer::min).get();//最小 28
System.out.println(mina);
System.out.println("=========第二种方式================");
double doublesum = list.stream().mapToDouble(Student::getAge).sum();//和
System.out.println(doublesum);
int intmax = list.stream().mapToInt(Student::getAge).max().getAsInt();//最大
System.out.println(intmax);
int intmin = list.stream().mapToInt(Student::getAge).min().getAsInt();//最小
System.out.println(intmin);
double avg = list.stream().mapToDouble(Student::getAge).average().getAsDouble();//平均
System.out.println(avg);
}
}
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
class Student{
int id;
String name;
int age;
}
public class ListTest03 {
@Test
public void test(
阅读背景：
list 的三种求和方式
来源：互联网
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