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根据指定字段#xff0c;获取两个对象集合的交集、补集、并集等将对象中的多个字段值#xff0c;抽取到一个List中
import java.lang.reflect.Field;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function…支持操作
根据指定字段获取两个对象集合的交集、补集、并集等将对象中的多个字段值抽取到一个List中
import java.lang.reflect.Field;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;/*** DescriptionList工具类。用于处理两个列表的交集、并集、差集等操作。** author jiangniao* date 2024-3-22*/
public class ListUtil {private ListUtil() {}/*** 提取多个字段的值到一个list** param list 对象集合* param fieldName 需要提取的字段名* return*/public static ListString extractFieldsToList(List? list, String... fieldName) {return list.stream().flatMap(item-Arrays.stream(fieldName).map(field-BeanUtils.getSimpleProperty(item, field))).collect(Collectors.toList());}/*** 根据指定字段找出两个列表的交集。** param list1* param list2* param fields* param T* return*/public static T ListT intersection(ListT list1, ListT list2, String... fields) {return list1.stream().filter(item1-containsWithFields(list2, item1, fields)).collect(Collectors.toList());}/*** 根据指定字段找出两个列表的并集** param list1* param list2* param fields* param T* return*/public static T ListT union(ListT list1, ListT list2, String... fields) {ListT union new ArrayList(list1);union.addAll(list2.stream().filter(item-!containsWithFields(list1, item, fields)).collect(Collectors.toList()));return union;}/*** 根据指定字段找出两个列表的差集。list1中有list2中没有的元素** param list1* param list2* param fields* param T* return 返回list1过滤后的数据*/public static T ListT difference(ListT list1, ListT list2, String... fields) {return list1.stream().filter(item-!containsWithFields(list2, item, fields)).collect(Collectors.toList());}/*** 找出两个列表的差集。list1中有list2中没有的元素。* p用于非Object对象的比较比如String、Integer等** param list1* param list2* param T* return 返回list1过滤后的数据*/public static T ListT difference(ListT list1, ListT list2) {list1.removeAll(list2);return list1;}/*** 辅助方法判断列表中是否包含指定对象** param list* param item* param fields* param T* return*/private static T boolean containsWithFields(ListT list, T item, String... fields) {return list.stream().anyMatch(item2-matchesFields(item, item2, fields));}/*** 辅助方法判断两个对象的指定字段是否相等** param item1* param item2* param fields* param T* return*/private static T boolean matchesFields(T item1, T item2, String... fields) {try {for (String field : fields) {Field declaredField1 item1.getClass().getDeclaredField(field);Field declaredField2 item2.getClass().getDeclaredField(field);declaredField1.setAccessible(true);declaredField2.setAccessible(true);if (!Objects.equals(declaredField1.get(item1), declaredField2.get(item2))) {return false;}}return true;} catch (Exception e) {throw new RuntimeException(e);}}/*** 根据指定字段对列表进行去重** param list* param fields* param T* return*/public static T ListT distinctByFields(ListT list, String... fields) {return list.stream().filter(distinctByKey(t-getKey(t, fields))).collect(Collectors.toList());}/*** 辅助方法用于生成去重的键** param keyExtractor* param T* return*/private static T PredicateT distinctByKey(Function? super T, ? keyExtractor) {MapObject, Boolean seen new ConcurrentHashMap();return t-seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) null;}/*** 辅助方法生成由指定字段的值组成的键** param item* param fields* param T* return*/private static T String getKey(T item, String... fields) {StringBuilder key new StringBuilder();try {for (String field : fields) {Field declaredField item.getClass().getDeclaredField(field);declaredField.setAccessible(true);key.append(declaredField.get(item)).append(-);}} catch (Exception e) {throw new RuntimeException(e);}return key.toString();}}
