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目录基于huffman编码特点建立的一个huffman编/译码器,并做了建立简单的可视化
效果图
编码结果图
压缩效果图
凹凸表可视化
二叉树可视化
问题重述
利用哈夫曼编码进行信息通信可以较大提高信道利用率,缩短信息传输时间,降低传输成本。但是,这要求在发送端通过一个编码系统对待传数据预先编码;在接收端将传来的数据进行译码(复原)。对于双工信道(即可以双向传输信息的信道),每端都需要一个完整的编/译码系统。试为这样的信息收发站写一个哈夫曼码的编译码系统。该系统应具有以下功能
- 初始化(Initialization)。从终端读入字符集大小n,及n个字符和m个权值,建立哈夫曼树,并将其保存于磁盘huffman文件中。
- 编码(Coding)。利用已建好的哈夫曼树(如不在内存,则从已保存的 huffman文件中读入),对带发送电文(读取自文件 tobetrans. dat)进行编码,然后将结果保存于磁盘文件codefile 中。
- 解码(Decoding)。利用已建好的哈夫曼树,对文件codefile中的代码进行译码,结果存入文件textfile中。
- 打印代码文件(Print)。将文件codefile显示在终端上,每行50个代码。同时将此字符形式的编码文件写人文件codeprint 中。
- 打印哈夫曼树(Tree printing)。将已在内存中的哈夫曼树以直观的方式(树或凹入表的形式显示在终端,同时将此字符形式的哈弗曼树写入文件treeprint
全局变量
static Map<Character, String> huffmanCodes = new HashMap<>()
static StringBuilder stringBuilder = new StringBuilder();
static Node huffmanTree
static String stringtree = "";
这里我们主要是定义一些全局变量方便后面使用:
- huffmancode :建立哈希表;
- stringBuilder :后面用于翻译huffman树;
- huffmanTree :huffman树的根节点;;
- huffmancode :建立哈希表;;
自定义List类型
static class MyList<Node> {
//定义Object类型的数组
Object[] data ;
//统计变量,用于统计数组元素的真实个数
int size;
public MyList() {
this(50);
}
MyList(int length){
data = new Object[length];
}
//长度
public int getLength(){
return size;
}
@Override
public String toString() {
//构建一个新的数组,长度为size
Object[] newdata = new Object[size];
//将data中的元素拷贝到新数组中
System.arraycopy(data, 0, newdata, 0, size);
//利用Arrays类,将数组转换成字符串
return Arrays.toString(newdata);
}
public void remove(Node obj){
int index = getFirstIndex(obj);
//System.out.println(index);
deleteElementByIndex(index);
}
public int getFirstIndex(Node obj){
for (int i = 0; i < size; i++) {
if(obj.equals(data[i])){
return i;
}
}
return -1;//没有找到
}
//删除指定索引处的元素
public void deleteElementByIndex(int index){
if(index<0||index>size){
throw new ArrayIndexOutOfBoundsException("数组越界了,索引范围是:0~"+(size-1));
}
System.arraycopy(data, index+1, data, index, size-index-1);
size--;
}
void add(Node obj){
//如果数组满了
if(size>=data.length){
//构建一个新的数组,容量默认增加10
Object[] newdata = new Object[data.length+10];
//将原来的数组内容拷贝到扩容后的数组中
System.arraycopy(data, 0, newdata, 0, size);
}
//将新增的元素添加在数组的末尾
data[size] = obj;
//数组真实长度自增1
size++;
}
public void sort()
{
Arrays.sort( data);
}
}
Node节点类型
这里采用了Comparable
class Node implements Comparable<Node> {
Character data; //存放数据
int weight; //权值,表示字符出现的次数
Node left;
Node right;
public Node() {
}
public Node(Character data, int weight) {
this.data = data;
this.weight = weight;
}
@Override
public int compareTo(Node o) {
return this.weight - o.weight;
}
}
导入字符集数据
利用Java的字典结构导入数据(利用字典来统计数据也是极快的),将导入的数据变成链表的样式,便于后面的树建立。
private static ArrayList<Node> getNodes() {
MyList<Node> rootnode1=new MyList<>();
ArrayList<Node> node_temp = new ArrayList<>();
//构建一个map等下存huffman编码
Map<Character, Integer> counts = new HashMap<>();
File zhifuji = new File("D:/Desktop/string.txt");
try {
BufferedReader bufferedReader = new BufferedReader(new FileReader(zhifuji));//把读取的数据给fr
String line;
while ((line = bufferedReader.readLine()) != null) {
String[] strArray = line.split("=");
counts.put(strArray[0].charAt(0), Integer.valueOf(strArray[1]));
}
} catch (FileNotFoundException e2) {
System.out.println("找不到指定文件");
System.exit(-1);
} catch (IOException e1) {
System.out.println("文件内容读取错误");
System.exit(-1);
}
System.out.println("字符集内容已导入");
//将统计来的每个键值对转成一个Node对象,并加入到nodes集合
//遍历map
System.out.println("输入结果展示结果:");
System.out.println(counts + "\n");
for (Map.Entry<Character, Integer> entry : counts.entrySet()) {
node_temp.add(new Node(entry.getKey(), entry.getValue()));
}
return node_temp;
}
建立huffman树
建立huffman树的规则
- 将所有左,右子树都为空的作为根节点
- 在森林中选出两根节点的权值最小的树作为一棵树的左,右子树,且置新树的附加根节点的权值为其左,右子树上根节点的权值之和,其中左子数的权值小于右子树的权值;
- 从森林中删除这两颗树,同时把新树加入到森林中;
- 重复2,3步骤,直到森林中只有一棵树为止,此树便是赫夫曼树
private static Node createHuffmanTree(List<Node> nodes) {
while (nodes.size() > 1) {
//利用collections的接口
Collections.sort(nodes);
Node leftNode = nodes.get(0);
Node rightNode = nodes.get(1);
Node parent = new Node(null, leftNode.weight + rightNode.weight);
parent.left = leftNode;
parent.right = rightNode;
nodes.remove(leftNode);
nodes.remove(rightNode);
nodes.add(parent);
}
//返回根节点
return nodes.get(0);
}
根据建立的huffman树构建出huffmancode
利用已经建立的huffman树和StringBuilder结构的特点,递归得到叶子结点,建立huffmancode
private static void gethuffmancode(Node node, String code, StringBuilder stringBuilder) {
StringBuilder stringBuilder2 = new StringBuilder(stringBuilder);
stringBuilder2.append(code);
if (node != null) {
//判断当前node是叶子节点还是非叶子节点
//因为非叶子结点的data为null
if (node.data == null) {
//说明是非叶子节点
//递归处理向左递归
//左0右1原则
gethuffmancode(node.left, "0", stringBuilder2);
//向右递归
gethuffmancode(node.right, "1", stringBuilder2);
} else {
//说明是叶子节点就表示找到了某个叶子节点最后
huffmanCodes.put(node.data, stringBuilder2.toString());
}
}
}
编码
利用我们之前得到huffmancode编码,进行编码。
private static StringBuilder zip(char[] bytes, Map<Character, String> huffmanCodes) {
//利用huffman编码表将传进来的byte数组转成huffman编码的字符串
StringBuilder stringBuilder = new StringBuilder();
for (char b : bytes) {
stringBuilder.append(huffmanCodes.get(b));
}
System.out.println("利用huffman编码得到二进制字符串:\n" + stringBuilder.toString());
return stringBuilder;
}
解码
因为huffman的前缀编码特点,进行解密
private static List<Character> decode(Map<Character, String> huffmanCodes, StringBuilder huffmanstring) {
System.out.println("huffman解码对应的二进制字符串:\n" + huffmanstring.toString());
//把字符串按照指定的huffman编码进行解
//因为把huffman编码表的k,v进行调换所以要反向查询
Map<String, Character> map = new HashMap<>();
for (Map.Entry<Character, String> entry : huffmanCodes.entrySet()) {
map.put(entry.getValue(), entry.getKey());
}
List<Character> list = new ArrayList<>();
for (int i = 0; i < huffmanstring.length(); ) {
int count = 1; //小的计数器
boolean flag = true;
Character b = null;//前缀编码不用担心弄错
//这里采用了贪心的策略,尽可能的匹配字节
while (flag) {
String key = huffmanstring.substring(i, i + count);
//System.out.println(key);
b = map.get(key);
if (b == null) {
count++;
} else {
flag = false;
}
}
list.add(b);
i += count; //匹配完毕,移动i
}
return list;
}
后续可视化
这里是有个问题,是无法解决的,就是下图的问题,就是可视化到后面,我们就会发现一个重合的问题,这里这是无法解决的,因为可视化的时候左图的右子树会向右延伸,右图的左子树会向左延伸,所以说这里的重合是不可避免的,我们只能尽量调整分支的角度使得整个重合尽可能的延缓重合
二叉树可视化
class Test extends JPanel {
Node root = HuffmanCode.gethuffmanTree();
public Test() {
// this.root = HuffmanCode.huffmanTree;
UI();
}
private void UI() {
System.out.println(root.data);
this.setLayout(new BorderLayout());
TreeView treeView = new TreeView();
add(treeView, BorderLayout.CENTER);
}
class TreeView extends JPanel {
private int radius = 20;
private int vGap = 50;
public void paintComponent(Graphics g) {
super.paintComponent(g);
if (root != null) {
display(g, root, getWidth() / 2, 30, getWidth() / 4);
}
}
private void display(Graphics g, Node root, int x, int y, int hGap) {
g.drawOval(x - radius, y - radius, 2 * radius, 2 * radius);
//画圆
g.drawString(root.data + "", x - 3, y + 2);//写值
//画线
if (root.left != null) {
connectLeftChild(g, x - hGap, y + vGap, x, y);
display(g, root.left, x - hGap, y + vGap, (int) (hGap / Math.pow(2, 1)));
}
if (root.right != null) {
connectRightChild(g, x + hGap, y + vGap, x, y);
display(g, root.right, x + hGap, y + vGap, (int) (hGap / Math.pow(2, 1)));
}
}
private void connectRightChild(Graphics g, int x1, int y1, int x2, int y2) {
// TODO Auto-generated method stub
double d = Math.sqrt((y2 - y1) * (y2 - y1) + (x2 - x1) * (x2 - x1));
int x11 = (int) (x1 - radius * (x1 - x2) / d);
int y11 = (int) (y1 - radius * vGap / d);
int x21 = (int) (x2 + radius * (x1 - x2) / d);
int y21 = (int) (y2 + radius * vGap / d);
g.drawLine(x11, y11, x21, y21);
}
private void connectLeftChild(Graphics g, int x1, int y1, int x2, int y2) {
// TODO Auto-generated method stub
double d = Math.sqrt(vGap * vGap + (x2 - x1) * (x2 - x1));
int x11 = (int) (x1 + radius * (x2 - x1) / d);
int y11 = (int) (y1 - radius * vGap / d);
int x21 = (int) (x2 - radius * (x2 - x1) / d);
int y21 = (int) (y2 + radius * vGap / d);
g.drawLine(x11, y11, x21, y21);
}
}
至此我们的huffman编码问题已经是几乎百分百解决了,下面我们给出总的main函数
public static void main(String[] args){
/* 第一步:判断文件huffmantree是否存在
第二步:根据字符集创建huffman树
第三步:根据huffman树生成对应的huffman编码,利用map的键对值很方便
第四步:根据huffman编码压缩,生成huffman字节数组
第四步:解码,根基huffmancode进行解码*/
File huffmanfile = new File("D:/Desktop/huffman.txt");
if (!huffmanfile.exists()) {
List<Node> nodes = getNodes();
huffmanTree = createHuffmanTree(nodes);
gethuffmancode(huffmanTree, "", stringBuilder);//得到huffman编码
//如果huffman code 不存在就写入
try {
String line = System.getProperty("line.separator");
StringBuilder str = new StringBuilder();
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(huffmanfile)); //把添加的内容添加到末尾
Set<Map.Entry<Character, String>> set = huffmanCodes.entrySet();
for (Map.Entry<Character, String> entry : set) {
str.append(entry.getKey()).append(":").append(entry.getValue()).append(line);
}
bufferedWriter.write(str.toString());
bufferedWriter.flush(); //清空缓存区
bufferedWriter.close();
} catch (FileNotFoundException e2) {
System.out.println("找不到指定文件");
System.exit(-1);
} catch (IOException e1) {
System.out.println("文件内容写入错误");
System.exit(-1);
}
System.out.println("huffmancode已写入");
} else {
try {
BufferedReader bufferedReader = new BufferedReader(new FileReader(huffmanfile));//把读取的数据给fr
String line;
while ((line = bufferedReader.readLine()) != null) {
String[] strArray = line.split(":");
huffmanCodes.put(strArray[0].charAt(0), strArray[1]);
}
} catch (FileNotFoundException e2) {
System.out.println("找不到指定文件");
System.exit(-1);
} catch (IOException e1) {
System.out.println("文件内容读取错误");
System.exit(-1);
}
System.out.println("huffmancode已导入");
}
//huffman树已建立
System.out.println("huffman编码表:");
System.out.println(huffmanCodes + "\n");
// System.out.println("请输入想要进行编码的字符串(目前只支持大写英文字符和-)");
// Scanner scanner = new Scanner(System.in);
// String content = scanner.nextLine();
StringBuilder content = new StringBuilder("");
try {
BufferedReader bufferedReader = new BufferedReader(new FileReader("D:/Desktop/tobetrans.dat"));//把读取的数据给fr
String line;
while ((line = bufferedReader.readLine()) != null) {
content.append(line);
}
} catch (FileNotFoundException e2) {
System.out.println("找不到指定文件");
System.exit(-1);
} catch (IOException e1) {
System.out.println("文件内容读取错误");
System.exit(-1);
}
System.out.println("content已导入");
char[] contentbytes = content.toString().toCharArray();
StringBuilder stringBuilder = zip(contentbytes, huffmanCodes);//压缩
try {
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("D:/Desktop/codefile.txt", false)); //把添加的内容添加到末尾
bufferedWriter.write(stringBuilder.toString());//写入编码的结果
bufferedWriter.flush(); //清空缓存区
bufferedWriter.close();
} catch (FileNotFoundException e2) {
System.out.println("找不到指定文件");
System.exit(-1);
} catch (IOException e1) {
System.out.println("文件内容写入错误");
System.exit(-1);
}
System.out.println();
System.out.println("压缩后的编码写入完成");
System.out.println("压缩后的结果: \n" + stringBuilder.toString());//解压
List<Character> decodecontent = decode(huffmanCodes, stringBuilder);//解压
try {
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("D:/Desktop/textfile.txt", false)); //把添加的内容添加到末尾
bufferedWriter.write(String.valueOf(decodecontent));//写入译码的结果
bufferedWriter.flush(); //清空缓存区
bufferedWriter.close();
} catch (FileNotFoundException e2) {
System.out.println("找不到指定文件");
System.exit(-1);
} catch (IOException e1) {
System.out.println("文件内容写入错误");
System.exit(-1);
}
System.out.println();
System.out.println("content解码后的文件写入完成");
System.out.println("解码后的字符串:");
try {
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("D:/Desktop/codeprint.txt", false)); //把添加的内容添加到末尾
int nextline = 0;
Iterator iterator = decodecontent.iterator();
while (iterator.hasNext()) {
nextline++;
Character temp = (Character) iterator.next();
System.out.print(temp);
bufferedWriter.write(temp);//写入译码的结果
if (nextline % 50 == 0) {
bufferedWriter.write("\n");
System.out.println();
}
}
bufferedWriter.flush(); //清空缓存区
bufferedWriter.close();
} catch (FileNotFoundException e2) {
System.out.println("找不到指定文件");
System.exit(-1);
} catch (IOException e1) {
System.out.println("文件内容写入错误");
System.exit(-1);
}
System.out.println();
System.out.println("50字符形式的文件写入完成");
JFrame jFrame = new JFrame("Tree GUI");
System.out.printf(String.valueOf(huffmanTree));
jFrame.add(new Test());
jFrame.setSize(1980, 1280);
jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jFrame.setLocationRelativeTo(null);
jFrame.setVisible(true);
File file = new File("D:/Desktop/huffman.txt");
if (file.exists()) {
file.delete();
System.out.println("删除成功");
}
Print(huffmanTree, "");
try {
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("D:/Desktop/treeprint.txt", false));
bufferedWriter.write(stringtree);
bufferedWriter.flush(); //清空缓存区
bufferedWriter.close();
} catch (FileNotFoundException e2) {
System.out.println("找不到指定文件");
System.exit(-1);
} catch (IOException e1) {
System.out.println("文件内容写入错误");
System.exit(-1);
}
}
链接: 完整代码下载链接.