基础集合工具类

1、工具类 CollectionUtils.java

    
    private static final String SEPARATOR = ",";

    
    public static  List listDistinct(List list, String... fieldNameArr) {
        //判断集合是否为空
        if (list==null && list.size()==0){
            return list;
        }
        
        //去重处理
        List resultList = list.stream()
                .collect(Collectors.collectingAndThen(Collectors.toCollection(() ->
                        new TreeSet<>(Comparator.comparing(o -> {
                            //遍历处理集合对象中的属性
                            StringBuilder builder = new StringBuilder();
                            for (String fieldName : fieldNameArr) {
                                //根据对象和字段名称获取get方法返回值
                                String value = BeanUtils.getMethodValue(o, fieldName);
                                builder.append(value).append(SEPARATOR);
                            }
                            return builder.toString();
                        }))), ArrayList::new));
        return resultList;
    }

2、引用工具类 BeanUtils.java

package com.pearl.common.spring;

import com.pearl.common.entity.User;


public class BeanUtils {
    
    private static final String GET_PREFIX = "get";

    
    private static final String SET_PREFIX = "set";

    
    public static  String getMethodValue(T t, String name) {
        String methodName = GET_PREFIX + name.substring(0, 1).toUpperCase() + name.substring(1);
        String value = "";
        try {
            value = String.valueOf(t.getClass().getMethod(methodName).invoke(t));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return value;
    }

    public static void main(String[] args) {
        //根据对象和字段名称获取get方法返回值
        User user = new User("1", "张三", 18);
        String nameVale = getMethodValue(user, "name");
        System.out.printf("name：" + nameVale);

    }

}

3、引用实体 User.java

package com.pearl.common.entity;


public class User {

    
    private String id;
    
    private String name;
    
    private Integer age;

    public String getId() {
        return id;
    }

    public void setId(String 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 User(String id, String name, Integer age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "id='" + id + ''' +
                ", name='" + name + ''' +
                ", age=" + age +
                '}';
    }
}

4、功能测试

        //通过反射对List集合中对象的属性进行去重
        List userList = new ArrayList<>();
        userList.add(new User("1","张三",18));
        userList.add(new User("3","李四",18));
        userList.add(new User("5","王五",18));
        userList.add(new User("2","张三",20));
        userList.add(new User("4","李四",18));

        System.out.println("去重前：");
        for (User user : userList) {
            System.out.println(user.toString());
        }

        //1.单属性去重(根据名称去重)
        List users1 = listDistinct(userList,"name");
        System.out.println("单属性去重(根据名称去重)后：");
        for (User user : users1) {
            System.out.println(user.toString());
        }

        //2.多属性去重(根据名称和年龄去重)
        List users2 = listDistinct(userList,"name","age");
        System.out.println("多属性去重(根据名称和年龄去重)后：");
        for (User user : users2) {
            System.out.println(user.toString());
        }

结果