用Java编写显示哈夫曼树的树形结构的代码

以下是一个用Java编写的显示哈夫曼树树形结构的简单示例代码：

import java.util.PriorityQueue;

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

    public HuffmanNode(char c, int frequency) {
        this.c = c;
        this.frequency = frequency;
    }

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

public class HuffmanTreeDisplay {
    public static void main(String[] args) {
        String text = "Hello, world!";
        HuffmanNode root = buildHuffmanTree(text);

        displayHuffmanTree(root, "");
    }

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

        PriorityQueue<HuffmanNode> pq = new PriorityQueue<>();
        for (int i = 0; i < frequency.length; i++) {
            if (frequency[i] > 0) {
                pq.offer(new HuffmanNode((char) i, frequency[i]));
            }
        }

        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.offer(parent);
        }

        return pq.poll();
    }

    public static void displayHuffmanTree(HuffmanNode root, String prefix) {
        if (root == null) {
            return;
        }

        if (root.left == null && root.right == null) {
            System.out.println(root.c + " -> " + prefix);
        }

        displayHuffmanTree(root.left, prefix + "0");
        displayHuffmanTree(root.right, prefix + "1");
    }
}

这段代码实现了以下几个功能：
- `buildHuffmanTree` 函数根据输入的文本构建哈夫曼树。
- `displayHuffmanTree` 函数用于递归地显示哈夫曼树的树形结构，并打印每个字符对应的编码。

在 `main` 函数中，我们使用字符串 "Hello, world!" 来构建哈夫曼树，并显示其树形结构和字符编码。你可以根据自己的需求修改 `main` 函数中的文本内容。