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ListUtil类添加countMap方法✒️

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This commit is contained in:
大火yzs 2021-05-04 15:01:43 +08:00
parent 32e29438d7
commit a1dba4f36b
2 changed files with 51 additions and 8 deletions
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37
hutool-core/src/main/java/cn/hutool/core/collection/ListUtil.java
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@ -5,18 +5,12 @@ import cn.hutool.core.comparator.PropertyComparator;
import cn.hutool.core.convert.Convert;
import cn.hutool.core.lang.Editor;
import cn.hutool.core.lang.Matcher;
import cn.hutool.core.map.MapUtil;
import cn.hutool.core.util.ArrayUtil;
import cn.hutool.core.util.ObjectUtil;
import cn.hutool.core.util.PageUtil;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;
public class ListUtil {
@ -450,6 +444,33 @@ public class ListUtil {
return list2;
}
/**
* 统计list中元素出现次数
*
* @param list list容器
* @return Map<T, Long> 统计次数 如: {"hello":10}
* @since 5.6.5
*/
public static <T> Map<T, Long> countMap(List<T> list) {
Map<T, Long> countMap = MapUtil.newHashMap();
for (T o : list) {
countMap.put(o, countMap.getOrDefault(o, 0L) + 1);
}
return countMap;
//return list.stream().collect(Collectors.groupingBy(o -> o, Collectors.counting()));//stream方式
}
/**
* 统计list中元素出现次数
*
* @param list list容器
* @return Map<T, Long> 统计次数 如: {"hello":10}
* @since 5.6.5
*/
public static <T> Map<T, Long> countMap(List<T> list, boolean isValueDesc) {
return MapUtil.sortByValue(countMap(list), isValueDesc);
}
/**
* 获取匹配规则定义中匹配到元素的所有位置
*

22
hutool-core/src/test/java/cn/hutool/core/collection/ListUtilTest.java
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@ -10,6 +10,7 @@ import org.junit.Test;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
public class ListUtilTest {
@ -46,6 +47,27 @@ public class ListUtilTest {
Assert.assertEquals("edit3", filter.get(2));
}
@Test
@Ignore
public void countMapTest(){
List<String> list = new ArrayList<>();
list.add("AAA");
list.add("BBB");
list.add("AAA");
list.add("CCC");
list.add("DDD");
list.add("DDD");
//统计不排序
Map<?, Long> countMap = ListUtil.countMap(list);
Console.log(countMap);
//统计倒序排列
Map<String, Long> descCountMap = ListUtil.countMap(list, Boolean.TRUE);
Console.log(descCountMap);
//统计正序排列
Map<String, Long> ascCountMap= ListUtil.countMap(list, Boolean.FALSE);
Console.log(ascCountMap);
}
@Test
public void indexOfAll() {
List<String> a = ListUtil.toLinkedList("1", "2", "3", "4", "3", "2", "1");