用Java语言写的构造哈夫曼树和哈夫曼编码的实例

当然，我可以帮你提供一个用Java语言编写的构造哈夫曼树和哈夫曼编码的实例。以下是一个简单的实现：

import java.util.PriorityQueue;

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

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

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

public class HuffmanCoding {
    public static void main(String[] args) {
        String text = "Hello, World!";
        System.out.println("Original Text: " + text);

        // 构造哈夫曼树
        HuffmanNode root = buildHuffmanTree(text);

        // 生成哈夫曼编码
        String encodedText = encode(root, text);
        System.out.println("Encoded Text: " + encodedText);

        // 解码哈夫曼编码
        String decodedText = decode(root, encodedText);
        System.out.println("Decoded Text: " + decodedText);
    }

    public static HuffmanNode buildHuffmanTree(String text) {
        int[] frequency = new int[256];
        for (char c : text.toCharArray()) {
            frequency[c]++;
        }

        PriorityQueue<HuffmanNode> priorityQueue = new PriorityQueue<>();
        for (char c = 0; c < 256; c++) {
            if (frequency[c] > 0) {
                priorityQueue.add(new HuffmanNode(c, frequency[c]));
            }
        }

        while (priorityQueue.size() > 1) {
            HuffmanNode left = priorityQueue.poll();
            HuffmanNode right = priorityQueue.poll();

            HuffmanNode newNode = new HuffmanNode('\0', left.frequency + right.frequency);
            newNode.left = left;
            newNode.right = right;

            priorityQueue.add(newNode);
        }

        return priorityQueue.poll();
    }

    public static String encode(HuffmanNode root, String text) {
        StringBuilder encodedText = new StringBuilder();
        encodeHelper(root, text, encodedText);
        return encodedText.toString();
    }

    private static void encodeHelper(HuffmanNode node, String text, StringBuilder encodedText) {
        if (node == null) {
            return;
        }

        if (node.left == null && node.right == null && Character.isLetter(node.data)) {
            encodedText.append(node.data);
        }

        encodeHelper(node.left, text, encodedText);
        encodeHelper(node.right, text, encodedText);
    }

    public static String decode(HuffmanNode root, String encodedText) {
        StringBuilder decodedText = new StringBuilder();
        HuffmanNode current = root;

        for (char c : encodedText.toCharArray()) {
            if (c == '0') {
                current = current.left;
            } else {
                current = current.right;
            }

            if (current.left == null && current.right == null) {
                decodedText.append(current.data);
                current = root;
            }
        }

        return decodedText.toString();
    }
}

这个实例演示了如何构建哈夫曼树，并使用树来对给定的文本进行编码和解码。在这个例子中，我们首先统计给定文本中每个字符出现的频率，然后根据频率构造哈夫曼树。最后，使用哈夫曼树对原始文本进行编码，并将编码后的文本进行解码以还原原始文本。

希望这个实例可以帮助到你！如果你还有其他问题，请随时向我提问。