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处理Collectors遇到null的情况

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achao 2022-07-03 17:35:54 +08:00 committed by VampireAchao
parent 8af05e0892
commit 9538041ac5
2 changed files with 8 additions and 3 deletions
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7
hutool-core/src/main/java/cn/hutool/core/stream/CollectorUtil.java
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@ -2,6 +2,7 @@ package cn.hutool.core.stream;
import cn.hutool.core.lang.Opt;
import cn.hutool.core.text.StrUtil;
import cn.hutool.core.util.ArrayUtil;
import java.util.Collections;
import java.util.EnumSet;
@ -9,6 +10,7 @@ import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.List;
import java.util.Objects;
import java.util.StringJoiner;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
@ -104,7 +106,10 @@ public class CollectorUtil {
final BiConsumer<Map<K, A>, T> accumulator = (m, t) -> {
final K key = Opt.ofNullable(t).map(classifier).orElse(null);
final A container = m.computeIfAbsent(key, k -> downstreamSupplier.get());
downstreamAccumulator.accept(container, t);
if (ArrayUtil.isArray(container) || Objects.nonNull(t)) {
// 如果是数组类型，不需要判空，场景——分组后需要使用：java.util.stream.Collectors.counting 求null元素个数
downstreamAccumulator.accept(container, t);
}
};
final BinaryOperator<Map<K, A>> merger = mapMerger(downstream.combiner());
@SuppressWarnings("unchecked") final Supplier<Map<K, A>> mangledFactory = (Supplier<Map<K, A>>) mapFactory;

4
hutool-core/src/test/java/cn/hutool/core/collection/CollStreamUtilTest.java
View File

@ -153,7 +153,7 @@ public class CollStreamUtilTest {
// 对null友好
final Map<Long, Map<Long, Student>> termIdClassIdStudentMap = CollStreamUtil.group2Map(Arrays.asList(null, new Student(2, 2, 1, "王五")), Student::getTermId, Student::getClassId);
final Map<Long, Map<Long, Student>> termIdClassIdStudentCompareMap = new HashMap<Long, Map<Long, Student>>() {{
put(null, MapUtil.of(null, null));
put(null, MapUtil.empty());
put(2L, MapUtil.of(2L, new Student(2, 2, 1, "王五")));
}};
Assert.assertEquals(termIdClassIdStudentCompareMap, termIdClassIdStudentMap);
@ -215,7 +215,7 @@ public class CollStreamUtilTest {
new Student(1, 2, 1, "李四"));
final Map<Long, List<Student>> termIdStudentsMap = CollStreamUtil.groupBy(students, Student::getTermId, Collectors.toList());
final Map<Long, List<Student>> termIdStudentsCompareMap = new HashMap<>();
termIdStudentsCompareMap.put(null, Arrays.asList(null, null));
termIdStudentsCompareMap.put(null, Collections.emptyList());
termIdStudentsCompareMap.put(1L, Arrays.asList(new Student(1L, 1, 1, "张三"), new Student(1L, 2, 1, "李四")));
Assert.assertEquals(termIdStudentsCompareMap, termIdStudentsMap);