public class WordFrequency {
public static String sentence = "one three two two three three four four four";
public static Map<String,Integer> map;
public static void main(String[] args) {
map = new HashMap<>();
String[] words = sentence.split("\\s");
for (String word : words) {
Integer count = map.get(word);
if (count == null) {
count = 1;
} else {
++count;
}
map.put(word,count);
}
Comparator<String> myComparator = new Comparator<String>() {
@Override
public int compare(String s1,String s2) {
if (map.get(s1) < map.get(s2)) {
return -1;
} else if (map.get(s1) > map.get(s2)) {
return 1;
} else {
return 0;
}
}
};
SortedMap<String,Integer> sortedMap = new TreeMap<String,Integer>(myComparator);
System.out.println("Before sorting: " + map);
sortedMap.putAll(map);
System.out.println("After Sorting based on value:" + sortedMap);
}
}
输出：
Before sorting: {two=2,one=1,three=3,four=3}
After sorting based on value:{one=1,two=2,three=3}
预期产出：
{one=1,four=3,three=3}
解决方法
Note that @H_502_18@the ordering maintained by a tree map,like any sorted map,and whether or not an explicit comparator is provided,@H_502_18@must be consistent with equals if this sorted map is to correctly implement the Map interface. (See Comparable or Comparator for a precise definition of consistent with equals.) @H_502_18@This is so because the Map interface is defined in terms of the equals operation,but a sorted map performs all key comparisons using its compareTo (or compare) method,so @H_502_18@two keys that are deemed equal by this method are,from the standpoint of the sorted map,equal. The behavior of a sorted map is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Map interface.
您可以通过在值相等时比较键来解决此问题：
Comparator<String> myComparator = new Comparator<String>() {
@Override
public int compare(String s1,String s2) {
if (map.get(s1) < map.get(s2)) {
return -1;
} else if (map.get(s1) > map.get(s2)) {
return 1;
} else {
return s1.compareTo(s2);
}
}
};
这应该给你一个输出：
After sorting based on value:{one=1,three=3}
由于四个<三个基于字符串的自然顺序.
