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add CollStreamUtil

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This commit is contained in:
Looly 2024-09-29 16:19:07 +08:00
parent 5c163941fe
commit ede848ed07
2 changed files with 42 additions and 1 deletions
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22
hutool-core/src/main/java/org/dromara/hutool/core/collection/CollStreamUtil.java
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@ -29,6 +29,7 @@ import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.stream.Stream;
/**
* 集合的stream操作封装
@ -396,4 +397,25 @@ public class CollStreamUtil {
}
return map;
}
/**
* 笛卡尔积<br>
* 参考：https://www.baeldung-cn.com/java-cartesian-product-sets
*
* @param sets 集合列表
* @param index 索引
* @return 笛卡尔积
*/
public static Stream<List<Object>> cartesianProduct(final List<List<Object>> sets, final int index) {
if (index == sets.size()) {
return Stream.of(ListUtil.zero());
}
final List<Object> currentSet = sets.get(index);
return currentSet.stream().flatMap(element -> cartesianProduct(sets, index + 1)
.map(list -> {
final List<Object> newList = new ArrayList<>(list);
newList.add(0, element);
return newList;
}));
}
}

21
hutool-core/src/test/java/org/dromara/hutool/core/collection/CollStreamUtilTest.java
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@ -16,10 +16,10 @@
package org.dromara.hutool.core.collection;
import org.dromara.hutool.core.map.MapUtil;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.ToString;
import org.dromara.hutool.core.map.MapUtil;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
@ -320,6 +320,25 @@ public class CollStreamUtilTest {
}
}
@Test
void cartesianProductTest() {
final List<List<Object>> sets = new ArrayList<>();
sets.add(ListUtil.of(10, 20));
sets.add(ListUtil.of("John", "Jack"));
sets.add(ListUtil.of('I', 'J'));
final List<List<Object>> collect = CollStreamUtil.cartesianProduct(sets, 0).collect(Collectors.toList());
Assertions.assertEquals(8, collect.size());
Assertions.assertEquals("[10, John, I]", collect.get(0).toString());
Assertions.assertEquals("[10, John, J]", collect.get(1).toString());
Assertions.assertEquals("[10, Jack, I]", collect.get(2).toString());
Assertions.assertEquals("[10, Jack, J]", collect.get(3).toString());
Assertions.assertEquals("[20, John, I]", collect.get(4).toString());
Assertions.assertEquals("[20, John, J]", collect.get(5).toString());
Assertions.assertEquals("[20, Jack, I]", collect.get(6).toString());
Assertions.assertEquals("[20, Jack, J]", collect.get(7).toString());
}
/**
* 班级类
*/