2019/12/20--对象中某属性的求和

[lq920320]

public class ObjectPropertySumTest {


    @Data
    private class Student {
        private String name;
        private Integer age;
    }


    @Test
    public void objectPropertySum() {
        List<Student> students = buildTestData();
        // 7
        System.out.println(students.size());
        // 方式一：
        int ageSum1 = students.stream().mapToInt(Student::getAge).sum();
        // 70
        System.out.println("年龄总和" + ageSum1);
        // 方式二：
        int ageSum2 = students.stream().map(Student::getAge).reduce(Integer::sum).orElse(0);
        // 70
        System.out.println("年龄总和" + ageSum2);
    }

    private List<Student> buildTestData() {
        return new ArrayList<Student>() {{
            add(new Student() {{
                setName("A");
                setAge(10);
            }});
            add(new Student() {{
                setName("B");
                setAge(10);
            }});
            add(new Student() {{
                setName("C");
                setAge(10);
            }});
            add(new Student() {{
                setName("D");
                setAge(10);
            }});
            add(new Student() {{
                setName("E");
                setAge(10);
            }});
            add(new Student() {{
                setName("F");
                setAge(10);
            }});
            add(new Student() {{
                setName("G");
                setAge(10);
            }});
        }};

    }
}