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<>();
    //第一種方式
    userList.forEach(user2 -> {
      userIds.add(user2.getId());
      //這里可以進行更多的操作
    });
    System.out.println(userIds);
    //第二種方式
    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;
}