PriorityQueue Sort By Map Value with out Lambda (older version of Java)

Following problem require solution before jdk 1.8.
I have a string S="aab". All the character is put into HashMap based on their frequency. Now declaring a PriorityQueue with Comparator. So that all characters can be stored in the PriorityQueue in descending order base on the frequency. But I am getting the following error--

    Map<Character, Integer> dicT = new HashMap<>();        
    for(int i = 0;i < S.length(); i++) {           
       dicT.put(S.charAt(i), dicT.getOrDefault(S.charAt(i), 0) + 1);
    }
    PriorityQueue<Character> maxHeap = new PriorityQueue(
        new Comparator<Map.Entry<Character,Integer>>() {
            public int compare(Map.Entry<Character, Integer> entry1, 
                               Map.Entry<Character, Integer> entry2) {
                return entry2.getValue().compareTo(entry1.getValue());
            }
        });
        
    maxHeap.addAll(dicT.keySet());

Error(Using newer jdk to demonstrate problem only, the target jdk version is before jdk 1.8) ---

>java.lang.ClassCastException: class java.lang.Character
cannot be cast to class java.util.Map$Entry
(java.lang.Character and java.util.Map$Entry are in module
java.base of loader 'bootstrap') at line 14,
Solution$1.compare at line 659,
java.base/java.util.PriorityQueue.siftUpUsingComparator at line 636,
java.base/java.util.PriorityQueue.siftUp at line 329,
java.base/java.util.PriorityQueue.offer at line 310,
java.base/java.util.PriorityQueue.add at line 187,
java.base/java.util.AbstractQueue.addAll at line 22,
Solution.reorganizeString at line 54,
DriverSolution.helper at line 84,
Driver.main

But if I use lambda then it's working fine --

PriorityQueue<Character> maxHeap = new PriorityQueue(
        (x, y) -> dicT.get(y) - dicT.get(x));
    maxHeap.addAll(dicT.keySet());

Please help me how can I write the block of code with out lambda?

You are declaring a PriorityQueue<Character> which uses a Comparator<Character> to define priority. But you are providing a Comparator<Map.Entry<...>> hence the error. Give it a Comparator<Character> instead:

Comparator<Character> order = Comparator.comparingInt(dict::get).reversed();
PriorityQueue<Character> maxHeap = new PriorityQueue<>(order);

You can use an anonymous class instead of the Comparator static methods, though I really can't see any reason why you would.

I really appreciate for you help. This is not about my IDE. My work place does not allow us to use all the Oracle libraries. And project is too old. Using older version version of jdk. So we are not able to use any lambda or method reference. But I am able to figure out the solution.

1. Without Lambda --

   PriorityQueue<Character> maxHeap= new PriorityQueue(new Comparator<Character>(){           
   public int compare(Character c1, Character c2){
   return dicT.get(c2) - dicT.get(c1);
   }            
   });

2. With Lambda --

   PriorityQueue<Character> maxHeap =new PriorityQueue((x,y)->dicT.get(y)-dicT.get(x));

3. With Method Reference--

   PriorityQueue<Character> maxHeap = new PriorityQueue(Comparator.comparingInt(dicT::get).reversed());