Lambda如何实现字符串出现次数排序算法

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四种方式的执行时间比例大概是 100：50：15：12

/**
* Lambda+stream 排序
*/
public List useLambdaStream(){
List strList = Arrays.asList("a,b,cc,b,b,cc".split(","));
//
Map sortMap = strList.stream().collect(Collectors.groupingBy(t -> t, Collectors.counting()));
Map filterMap = new HashMap<>();
List sortList = strList.stream().filter(t -> null == filterMap.put(t, t)).collect(Collectors.toList());
sortList.sort((t1, t2) -> (int) (sortMap.get(t2) - sortMap.get(t1)));
return sortList;
}

/**
* Lambda 排序
*/
public List useLambda() {
List strList = Arrays.asList("a,b,cc,b,b,cc".split(","));
//
Map sortMap = new HashMap<>();
for (String s : strList) {
Integer count = sortMap.get(s);
if (null != count) {
sortMap.put(s, count + 1);
} else {
sortMap.put(s, 1);
}
}
//
List> entryList = new ArrayList<>(sortMap.entrySet());
entryList.sort((t1, t2) -> t2.getValue() - t1.getValue());
//
List listResult = new ArrayList<>();
for (Entry mapping : entryList) {
listResult.add(mapping.getKey());
}
return listResult;
}

/**
* Comparator 排序
*/
public List useComparator() {
List strList = Arrays.asList("a,b,cc,b,b,cc".split(","));
//
Map map = new TreeMap();
for (String key : strList) {
Integer value = map.get(key);
if (null == value) {
map.put(key, 1);
} else {
map.put(key, value + 1);
}
}
//
List> list = new ArrayList<>(map.entrySet());
Collections.sort(list, new Comparator>() {
@Override
public int compare(Entry o1, Entry o2) {
return o2.getValue().compareTo(o1.getValue());
}
});
//
List listResult = new ArrayList<>();
for (Entry mapping : list) {
listResult.add(mapping.getKey());
}
return listResult;
}

/**
* Comparable 排序
*/
public List useComparable(){
List strList = Arrays.asList("a,b,cc,b,b,cc".split(","));
//
List listOrder = new ArrayList<>();
for(String s : strList){
OrderAssist tmp = new OrderAssist(s, 1);
if(listOrder.contains(tmp)){
listOrder.get(listOrder.indexOf(tmp)).count++;
}else{
listOrder.add(tmp);
}
}
Collections.sort(listOrder);
//
List listResult = new ArrayList<>();
for(OrderAssist object : listOrder){
listResult.add(object.name);
}
return listResult;
}

//comparable辅助类
class OrderAssist implements Comparable{
public String name;
public int count;

public OrderAssist(String name, int count){
this.name = name;
this.count = count;
}
@Override
public boolean equals(Object object){
return this.name.equals(((OrderAssist)object).name);
}
@Override
public int compareTo(OrderAssist entity) {
return entity.count - count;
}
}

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