Give a string ① please count the number of times each letter appears ② please print the pair with the most letters

1.       According to the title , First of all, I thought of two methods . One is to use a hash table , The other is to use Map Collection to store < character , Number > The key/value pair .

The first method ：

public class StringTest {
    /* Set a static hash array , We all know that every letter corresponds to a askii Code value ,
     Put alphabetic askII Code value as subscript , When traversing it , Its value is increased by one .
     example ：a Of ascii The code value is 65, When traversing it , take arr[65]++;*/
    static int[] hash = new int[255];
    public static void main(String[] args) {
        String str = "ksjhfkjashfkahfkahfiuuytwurekahd";
        // Traverse each character of the string 
        for(int i = 0;i<str.length();i++){
            char c = str.charAt(i);
            hash[c]++;
        }
        int max = 0;
        // Find the maximum number of occurrences 
        for(int i:hash){
            if(i>max)
                max = i;
        }
        // When hash There is a value in the array equal to max, Then print the character corresponding to its subscript 
        for(int i = 0;i<hash.length;i++){
            if(hash[i]==max){
                System.out.println(Character.toChars(i));
            }
        }
    }
}

The second method ：

    public static void main(String[] args) {
        String str = "ksjhfkjashfkahfkahfiuuytwurekahd";
        HashMap<Character,Integer> hm = new HashMap<>();
        Set<Character> charSet = hm.keySet();
        /* Traversal string , If charSet There is this element , It's in hm Add the key value of this element 1;
         If charSet There is no such element , Then take this value as the key , And assign its value to 1, Added to the hm in */
        for(int i = 0;i<str.length();i++){
            char c = str.charAt(i);
            if(!charSet.contains(c)){
                hm.put(c,1);
            }else{
                int num = hm.get(c);
                num++;
                hm.put(c,num);
            }
        }
        
        // take hm Set the value of the key value pair of in a set and traverse to find the maximum value 
        int max = 0;
        for(Integer i:hm.values()){
            if(i>max)
                max = i;
        }
        
        // Traverse HashMap The elements in , Set the value equal to max Key output of 
        Set<Map.Entry<Character, Integer>> sme = hm.entrySet();
        for(Map.Entry<Character,Integer> me:sme){
            if(me.getValue()==max){
                System.out.println(me.getKey());
            }
        }
    }
}