Java8 使用流抽取List＜T＞ 集合中T的某个属性操作

import lombok.AllArgsConstructor;

import lombok.Data;

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Collectors;

/**

  * @author lanfangyi

  * @version 1.0

  * @since 2019/5/12 13:22

  */

@Data

@AllArgsConstructor

public class User {

   private Long id;

   private String name;

}

class TestMainService {

   public static void main(String[] args) {

     List<User> userList = new ArrayList<>();

     User user = new User(1L, "zhangsan" );

     User user1 = new User(2L, "lisi" );

     userList.add(user);

     userList.add(user1);

     List<Long> userIds = new ArrayList<>();

     //第一种方式

     userList.forEach(user2 -> {

       userIds.add(user2.getId());

       //这里可以进行更多的操作

     });

     System.out.println(userIds);

     //第二种方式

     List<Long> userIds2 = userList.stream().map(User::getId).collect(Collectors.toList());

     System.out.println(userIds2);

   }

}

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Object obj = CollectionUtils.find(UserList.get(),

new BeanPropertyValueEqualsPredicate( "id" , "9587" ));

if (obj == null ){

   log.info( "not found" );

} else {

   //do your thing

}

public static <T> T findElementByPropertyValue(List<T> list, String propertyName, Object value) throws Exception {

   if (list == null || list.isEmpty()) {

     return null ;

   }

   PropertyDescriptor pd = new PropertyDescriptor(propertyName, list.get( 0 ).getClass());

   for (T t : list) {

     Object obj = pd.getReadMethod().invoke(t);

     if (StringUtils.equals(String.valueOf(value), String.valueOf(obj))) {

       return t;

     }

   }

   return null ;

}