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This article mainly introduces Lambda how to achieve string occurrence sorting algorithm, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let Xiaobian take you to understand.

The proportion of execution time of the four modes is about 100, 50, 15, 12.

/ * *

* Lambda+stream sorting

, /

Public List useLambdaStream () {

List strList = Arrays.asList ("a _" .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)) .birthday (Collectors.toList ())

SortList.sort ((T1, T2)-> (int) (sortMap.get (T2)-sortMap.get (T1))

Return sortList

}

/ * *

* Lambda sorting

, /

Public List useLambda () {

List strList = Arrays.asList ("a _" .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 sorting

, /

Public List useComparator () {

List strList = Arrays.asList ("a _" .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 sorting

, /

Public List useComparable () {

List strList = Arrays.asList ("a _" .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 helper class

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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