com.github.dennisit.vplus.data.utils.CollectionUtils Maven / Gradle / Ivy
/*--------------------------------------------------------------------------
* Copyright (c) 2010-2020, Elon.su All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* Neither the name of the elon developer nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
* Author: Elon.su, you can also mail [email protected]
*--------------------------------------------------------------------------
*/
package com.github.dennisit.vplus.data.utils;
import com.google.common.base.Function;
import com.google.common.collect.Maps;
import java.util.*;
import java.util.stream.Collectors;
/**
* Created by Elon.su on 17/5/29.
*/
public class CollectionUtils{
/**
* 集合是否为空
* @param coll 目标集合
* @return 不为空返回true
*/
public static boolean isNotEmpty(final Collection coll){
return !isEmpty(coll);
}
/**
* 集合是否为空
* @param coll 目标集合
* @return 为空返回true
*/
public static boolean isEmpty(final Collection coll){
return org.apache.commons.collections4.CollectionUtils.isEmpty(coll);
}
/**
* 进行map集合中相同元素的value值聚合
* @param target 目标Map
* @param multis 往目标Map上追加的多个Map
* @param 泛型约束Key
* @param 泛型约束Map
* @return 多个mapKey聚合后的结果, key相同的元素, value值进行合并
*/
public static Map> keyMerged(Map> target, Map>... multis){
Map> base = Optional.ofNullable(target).orElse(Maps.newHashMap());
// 待追加的多个map元素
List>> adding = Arrays.stream(multis)
.map(x -> {
return Optional.ofNullable(x).orElse(Maps.newHashMap());
})
.collect(Collectors.toList());
// 逐个Map元素追加
adding.forEach(x ->{
x.keySet().forEach(
key -> base.merge(key, x.get(key), (v1, v2)
-> Arrays.asList(v1, v2).stream().flatMap(Collection::stream).collect(Collectors.toList())
)
);
});
return base;
}
/**
* 对list元素进行转化。
* @param srcList 源list
* @param fun 转换函数
* @param 源类型
* @param 目标类型
* @return 转换后的list
*/
public static List transform(Collection srcList, Function fun) {
if (isEmpty(srcList)) {
return Collections.EMPTY_LIST;
}
List descList = new ArrayList<>(srcList.size());
srcList.forEach(x -> {
descList.add(fun.apply(x));
});
return descList;
}
/**
* Map按照Value进行排期
* @param map 目标map
* @param key元素
* @param value元素
* @return 排序后的结果
*/
public static > Map sortByValue(Map map) {
List> list = new LinkedList>(map.entrySet());
Collections.sort(list, new Comparator>() {
@Override
public int compare(Map.Entry o1, Map.Entry o2) {
return (o1.getValue()).compareTo(o2.getValue());
}
});
Map result = new LinkedHashMap();
for (Map.Entry entry : list) {
result.put(entry.getKey(), entry.getValue());
}
return result;
}
}