Huffman.java

import java.util.*;class NodeHuffman {    int freq;    char character;    NodeHuffman left;    NodeHuffman right;}class MinComparator implements Comparator<NodeHuffman> {    @Override    public int compare(NodeHuffman x, NodeHuffman y)    {        return x.freq - y.freq;    }}public class Huffman {    public static HashMap<Character,String> cipher= new HashMap<Character,String>();    public static void printCode(NodeHuffman root, String s)    {        if (root.left == null && root.right == null && Character.isLetter(root.character)) {            cipher.put(root.character,s);            System.out.println(root.character + ":" + s);            return;        }        printCode(root.left, s + "0");        printCode(root.right, s + "1");    }    // main function    public static void main(String[] args)    {        Scanner in = new Scanner(System.in);        System.out.println("Enter a String that needs to be encoded to Huffman Code     :");        String input = in.nextLine();        HashMap<Character,Integer> map = new HashMap<Character, Integer>();        for (int i =0; i< input.length(); i++){            char currentChar = input.charAt(i);            Integer val = map.get(currentChar);            if (val == null)                map.put(currentChar, 0);            else                map.put(currentChar,val+1);        }        Object[] charArray = map.keySet().toArray();        Object[] charfreq = map.values().toArray();        PriorityQueue<NodeHuffman> queue = new PriorityQueue<NodeHuffman>(charArray.length, new MinComparator());        for (int i = 0; i < charArray.length; i++) {            NodeHuffman tempNode = new NodeHuffman();            tempNode.character = (char)charArray[i];            tempNode.freq = (int)charfreq[i];            tempNode.left = null;            tempNode.right = null;            // PUSH the node to queue            queue.add(tempNode);        }        // create a root node        NodeHuffman root = null;        while (queue.size() > 1) {            NodeHuffman elem1 = queue.peek();            queue.poll();            NodeHuffman elem2 = queue.peek();            queue.poll();            NodeHuffman newRoot = new NodeHuffman();            newRoot.freq = elem1.freq + elem2.freq;            newRoot.character = '-';            newRoot.left = elem1;            newRoot.right = elem2;            root = newRoot;            queue.add(newRoot);        }        System.out.println("____________________________________________________");        System.out.println("Generated Cipher    :");        printCode(root, "");        System.out.println("____________________________________________________");        System.out.println("Encoded String is :");        Object[] values = cipher.values().toArray();        for (int i = 0;i<input.length();i++){            char currentChar = input.charAt(i);            System.out.print(cipher.get(currentChar)+" "); // The space is just for visual clarity        }    }}