Java to find the highest frequency character in a string

The previous period of contact with this topic, generally understand, there are still some small places to further taste, for the time being noted.

Importjava.util.ArrayList;Importjava.util.Arrays;Importjava.util.Collection;ImportJava.util.HashMap;ImportJava.util.HashSet;ImportJava.util.Map;ImportJava.util.Set;/** Find the most frequently occurring characters in a string * main idea: first put the string into the set set to ensure that there are no duplicate characters * and then take out each character in the set set and index it with the indexof () method of String * If the index is not-1, the character exists, remember Record its index position in the string * and the variable + + that records the number of occurrences of the character, and then index from the current index position +1, * until the index value is-1, exit the loop, and the frequency at which each character appears is recorded * Next use map to store the frequency of characters and characters * The values of map are then formed into a ArrayList set * The maximum frequency calculated is compared to the value in map * If equal, it is the maximum frequency of the character*/  Public classHighfrequencyword { Public Static voidFindfrequencyword (String str) {Collection<Integer> al=NewArraylist<integer>(); Map<String,Integer> map=NewHashmap<string,integer>(); String TempStr= str;//Temporary storage stringstring[] Stringarray = Str.split ("");//cut a string into characters//to store characters that appear in a string without repeatingSet<string> set =NewHashset<string>(); intStringlength =stringarray.length;  for(inti = 0; i < stringlength; i++) {Set.add (stringarray[i]); }                 //remove a null character from the set (which one?) What do you mean?? )Set.remove (""); SYSTEM.OUT.PRINTLN (set);//the output here is [, A, B, c]                intCount = 0; BooleanFlag =true;  for(String s:set) { while(flag) {if(Tempstr.indexof (s)! =-1) {//if the index exists                    intindex = Tempstr.indexof (s);//record the current position of the characterTempStr = tempstr.substring (index + 1);//Continue queryingcount++; } Else{flag=false;//If the index does not exist, assign false to exit the loop}} Flag=true;//in order to perform the next loopMap.put (S,count);//record characters and their corresponding frequencies, and store them in a map//Initialize the results to prepare for the next cycleCount = 0; TempStr=str; }                 //Convert the value of map to a listAl=map.values (); //To the array againInteger[] Stringcount =al.toarray (Newinteger[]{}); Arrays.sort (stringcount);//Sort by Ascending                intCountlength=stringcount.length; intMAX=STRINGCOUNT[COUNTLENGTH-1];//get the maximum value of the array (the last one is the most frequently occurring value from small to large)                 for(String s:set) { for(inti=0; i<countlength; i++){                 //if the map value is the same as the maximum value, the output                if(Map.get (s) = =max) {System.out.println (S+ ":" + max);//Q: So the loop result will be output three times, how to output only once??                 }             }         }            }          Public Static voidMain (string[] args) {Findfrequencyword ("Abab BC"); } } 

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Java to find the highest frequency character in a string