博客

public class test {
    public static void main(String[] args) throws InterruptedException {
        List<Member> list1 = new ArrayList<>();
        List<Member> list2 = new ArrayList<>();
        for (int i = 0; i < 30000; i++) {
            Date date = new Date();
            //每个元素有名字
            list1.add(new Member((i + 1), "技术客", (i + 1), date));
            if (i % 2 == 0) {
                //对2取模无名字
                list2.add(new Member((i + 1), null, (i + 1), date));
            }
        }

        //双for循环嵌套测试
        long s1 = System.currentTimeMillis();
        int forNumber = 0;
        for (Member m2 : list2) {
            if (m2.getName() == null) {
                for (Member m1 : list1) {
                    if (m1.getId().intValue() == m2.getId().intValue()) {
//                      System.out.println(m2.getId()+" Name 值为空!!!");
                        forNumber++;
                    }
                }
            }
        }
        long s2 = System.currentTimeMillis();
        System.out.println("双for循环查询时间为：" + (s2 - s1) + "(毫秒)，一共查询出" + forNumber + "条数据 \n\n\n");
        //TimeUnit.SECONDS.sleep(3);

        //map查询测试
        long s3 = System.currentTimeMillis();

        int mapNumber = 0;
        Map<Integer, Member> map = new HashMap<>();
        for (Member m1 : list1) {
            map.put(m1.getId(), m1);
        }
        for (Member m2 : list2) {
            if (m2.getName() == null) {
                Member m = map.get(m2.getId());
                if (m != null) {
//                  System.out.println(m2.getId()+" Name 值为空!!!");
                    mapNumber++;
                }
            }
        }
        long s4 = System.currentTimeMillis();
        System.out.println("使用map结构查询时间为：" + (s4 - s3) + "(毫秒)，一共查询出" + mapNumber + "条数据 \n\n\n");



		//stream流方法1
		for (Person e1 : list1) {
            list2.stream().anyMatch(e2 -> {
                if (e1.getId() == e2.getId()) {
                    e1.setName(e2.getName());
                }
                return false;
            });
        }
        //stream流方法1
        list1.stream().forEach(e1 -> list2.stream().anyMatch(e2 -> {
            if (e1.getId() == e2.getId()) {
                e1.setName(e2.getName());
            }
            return false;
        }));
        System.out.println(list1);
    }
}

class Member {
    private Integer id;
    private String name;
    private Integer age;
    private Date addDate;

    public Member() {
    }

    public Member(Integer id, String name, Integer age, Date addDate) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.addDate = addDate;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Date getAddDate() {
        return addDate;
    }

    public void setAddDate(Date addDate) {
        this.addDate = addDate;
    }

}