【发布时间】：2012-11-25 09:17:53
【问题描述】：
我正在开发一个霍夫曼编码程序，我几乎完成了，但我陷入了无限递归循环。有谁知道这是哪里出错了？
这是我得到的错误：
Exception in thread "main" java.lang.StackOverflowError
at sun.nio.cs.SingleByteEncoder.encodeLoop(SingleByteEncoder.java:130)
at java.nio.charset.CharsetEncoder.encode(CharsetEncoder.java:544)
at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:252)
at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:106)
at java.io.OutputStreamWriter.write(OutputStreamWriter.java:190)
at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:111)
at java.io.PrintStream.write(PrintStream.java:476)
at java.io.PrintStream.print(PrintStream.java:619)
at java.io.PrintStream.println(PrintStream.java:756)
at HuffmanNode.buildTree(hw4.java:63)
at HuffmanNode.buildTree(hw4.java:64)
at HuffmanNode.buildTree(hw4.java:64)
at HuffmanNode.buildTree(hw4.java:64)
at HuffmanNode.buildTree(hw4.java:64)
at HuffmanNode.buildTree(hw4.java:64)
at HuffmanNode.buildTree(hw4.java:64)
at HuffmanNode.buildTree(hw4.java:64)
并且输出是不断的 5:1, 5:4, 5:2, 重复
我的数据文件如下所示：
a
a
a
a
d
d
d
d
d
d
d
d
k
k
k
k
k
k
f
f
f
f
f
f
h
h
h
h
h
h
b
b
b
b
b
b
b
b
n
n
n
n
n
n
n
e
e
e
e
e
i
i
i
i
i
i
i
i
l
k
j
a
n
s
g
l
k
j
a
s
v
o
i
j
a
s
d
l
k
g
k
n
m
a
s
d
k
l
o
v
h
a
s
d
g
z
我的代码是
import java.util.*;
import java.io.*;
class HuffmanNode implements Comparable<HuffmanNode>{
HuffmanNode right;
HuffmanNode left;
HuffmanNode parent;
int count;
String letter;
public HuffmanNode(){}
public HuffmanNode (String letter, int count){
this.letter = letter;
this.count = count;
}
public HuffmanNode (String letter, int count, HuffmanNode parent, HuffmanNode left, HuffmanNode right){
this.letter = letter;
this.count = count;
this.left = left;
this.right = right;
this.parent = parent;
}
public void setCount(int count){
this.count = count;
}
public int getCount(){
return count;
}
public void setRight(HuffmanNode right){
this.right = right;
}
public HuffmanNode getRight(HuffmanNode right){
return right;
}
public void setLeft(HuffmanNode left){
this.left = left;
}
public HuffmanNode getLeft(HuffmanNode left){
return left;
}
public void setParent(HuffmanNode right){
this.left = left;
}
public HuffmanNode getParent(HuffmanNode parent){
return parent;
}
public void buildTree(HuffmanNode node){
if (node.compareTo(this) <= 0 && left != null){
System.out.println(node.getCount() + ":" + this.count);
left.buildTree(node);
}
else if (node.compareTo(this) <= 0 && left == null){
this.left = node;
node.parent = this;
}
else if (node.compareTo(this) > 0 && right != null){
System.out.println(node.getCount() + ":" +this.count);
right.buildTree(node);
}
else if (node.compareTo(this) > 0 && right == null){
this.right = node;
node.parent = this;
}
}
public int compareTo(HuffmanNode x){
return this.count - x.count;
}
public void genCode(String s){
if(left != null){
left.genCode(s + "0");
}
if(right != null){
right.genCode(s + "1");
}
if (left == null && right == null){
System.out.println(s);
}
}
}
public class hw4{
public static void main (String []args)throws IOException{
//ask user to enter file name
System.out.printf("Enter a file location and name to encode [press Enter]: ");
Scanner input = new Scanner(System.in);
String filename = input.next();
//Gets file name from Scanner and checks to see if valid
File file = new File(filename);
//if (!file.isFile()){
//System.out.printf("Enter a file location and name to encode [press Enter]: ");
//}
Scanner text = new Scanner(file);
String[] letters = {"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};
int[] freq = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
String letter;
String tempStr;
int tempInt;
while(text.hasNext()){
letter = text.next();
//System.out.printf("%s\n", letter);
char c = letter.charAt(0);
int index = c - 97;
freq[index]++;
}
for(int i=0; i <25; i++){
System.out.printf("%s:%d\n", letters[i], freq[i]);
}
System.out.printf("\n");
for (int n=0; n <25; n++) {
for (int i=0; i <25; i++) {
if (freq[i] > freq[i+1]) {
// exchange elements
tempInt = freq[i];
tempStr = letters[i];
freq[i] = freq[i+1];
letters[i] = letters[i+1];
freq[i+1] = tempInt;
letters[i+1] = tempStr;
}
}
}
PriorityQueue<HuffmanNode> huffmanList = new PriorityQueue<HuffmanNode>();
for(int i=0; i <26; i++){
System.out.printf("%s:%d\n", letters[i], freq[i]);
if(freq[i] > 0){
huffmanList.add(new HuffmanNode(letters[i],freq[i]));
}
}
HuffmanNode root = new HuffmanNode();
while(huffmanList.size() > 1){
HuffmanNode x = huffmanList.poll();
HuffmanNode y = huffmanList.poll();
HuffmanNode result = new HuffmanNode("-", x.getCount() + y.getCount(), null, x, y);
if(root == null){
root = result;
}
else{
root.buildTree(result);
}
huffmanList.add(result);
}
root.genCode(" ");
}
}
【问题讨论】：
标签： java encoding recursion huffman-code