关于字符串

import java.util.*;

public class Main{
    public static void main(String [] args)
    {
        Scanner sc=new Scanner(System.in);
        while(sc.hasNext())
        {
            char[] words=sc.nextLine().toCharArray();
            Map<String,Integer> map=new HashMap<>();
            for(char c:words)
            {
                String temp=String.valueOf(c);
                if((c>=‘a‘&&c<=‘z‘)||(c>=‘A‘&&c<=‘Z‘)||(c>=‘0‘&&c<=‘9‘)||(c==‘ ‘)){
                if(map.keySet().contains(temp))
                {
                    map.put(temp,map.get(temp)+1);
                }else{
                    map.put(temp,1);
                }
                }

            }
            List<Map.Entry<String,Integer>> list=new ArrayList<>(map.entrySet());
            Collections.sort(list, new Comparator<Map.Entry<String,Integer>>(){
                @Override
                public int compare(Map.Entry<String,Integer> o1, Map.Entry<String,Integer> o2)
                {
                    if(o1.getValue()<o2.getValue())
                    {
                        return 1;
                    }else{
                        if(o1.getValue()==o2.getValue())
                        {
                            return o1.getKey().compareTo(o2.getKey());
                        }
                        else
                        {
                            return -1;
                        }
                    }
                }
            });
            
            for(Map.Entry<String,Integer> entry:list)
            {
                System.out.print(entry.getKey());
            }
            System.out.println();
        }
    }
}