哈夫曼编码java代码

哈夫曼编码是一种用于数据压缩的算法，它通过将出现频率较高的字符用较短的编码表示，从而实现对数据的压缩。下面是一个简单的哈夫曼编码的Java代码示例：

import java.util.*;

class HuffmanNode implements Comparable<HuffmanNode> {
    char data;
    int frequency;
    HuffmanNode left, right;

    public HuffmanNode(char data, int frequency) {
        this.data = data;
        this.frequency = frequency;
        left = right = null;
    }

    public int compareTo(HuffmanNode node) {
        return this.frequency - node.frequency;
    }
}

public class HuffmanCoding {
    public static void main(String[] args) {
        String text = "Hello, World!";
        Map<Character, Integer> frequencyMap = buildFrequencyMap(text);
        HuffmanNode root = buildHuffmanTree(frequencyMap);
        Map<Character, String> huffmanCodes = buildHuffmanCodes(root);

        System.out.println("Huffman Codes:");
        for (Map.Entry<Character, String> entry : huffmanCodes.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }

    private static Map<Character, Integer> buildFrequencyMap(String text) {
        Map<Character, Integer> frequencyMap = new HashMap<>();
        for (char c : text.toCharArray()) {
            frequencyMap.put(c, frequencyMap.getOrDefault(c, 0) + 1);
        }
        return frequencyMap;
    }

    private static HuffmanNode buildHuffmanTree(Map<Character, Integer> frequencyMap) {
        PriorityQueue<HuffmanNode> pq = new PriorityQueue<>();
        for (Map.Entry<Character, Integer> entry : frequencyMap.entrySet()) {
            pq.add(new HuffmanNode(entry.getKey(), entry.getValue()));
        }

        while (pq.size() > 1) {
            HuffmanNode left = pq.poll();
            HuffmanNode right = pq.poll();
            HuffmanNode parent = new HuffmanNode('\0', left.frequency + right.frequency);
            parent.left = left;
            parent.right = right;
            pq.add(parent);
        }

        return pq.poll();
    }

    private static Map<Character, String> buildHuffmanCodes(HuffmanNode root) {
        Map<Character, String> huffmanCodes = new HashMap<>();
        buildHuffmanCodesRecursive(root, "", huffmanCodes);
        return huffmanCodes;
    }

    private static void buildHuffmanCodesRecursive(HuffmanNode node, String code, Map<Character, String> huffmanCodes) {
        if (node == null) {
            return;
        }

        if (node.left == null && node.right == null) {
            huffmanCodes.put(node.data, code);
        }

        buildHuffmanCodesRecursive(node.left, code + "0", huffmanCodes);
        buildHuffmanCodesRecursive(node.right, code + "1", huffmanCodes);
    }
}

这段代码实现了哈夫曼编码的基本功能，包括构建字符频率映射、构建哈夫曼树和生成哈夫曼编码。你可以根据需要进行修改和扩展。