decompressfile.java

根据huffman树的一个压缩程序

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import javax.swing.*;

//解压缩类
public class DecompressFile {
	private int fileLength;//中文文件byte长度
	//读出头文件的频率
	private int[] inputFrequencies(DataInputStream fin) throws IOException{
		int []freq=new int[256];
		for(int j=0; j<256; j++){
			freq[j]=fin.readInt();
			fileLength+=freq[j];}
		System.out.print(fileLength);
		return freq;
	}
	//根据压缩编码寻找原文件对应字符并输出
	private void outputChar(DataInputStream fin,DataOutputStream fout,HuffmanNode root)throws IOException{
		HuffmanNode hn=root;
		int intreader,m,i;
		try{
			while(fileLength>0){//如果超过文件长度就不做循环
				intreader=fin.readInt();
				i=31;
				while(i>=0){
					if(hn.left==null&&hn.right==null){//对叶子节点写入对应字符
						fout.writeByte(hn.sign+256);
						fileLength--;//文件长度减一
						hn=root;//节点指向头节点
					}
					else{
						m=(intreader>>i)&1;//每次取出一个bit
						i--;//决定是向节点的左或者右寻找叶子
						if(m==1)	hn=hn.left;
						else	hn=hn.right;
					}
				}
			}
		}catch(IOException e){
		}
		fout.close();//关闭文件流
		fin.close();
		JOptionPane.showMessageDialog(null, "解压缩成功", "解压提示",JOptionPane.INFORMATION_MESSAGE);
		
	}
	//处理数据
	public void decompress(String output,String input){
		try{
			DataInputStream fin=new DataInputStream(new BufferedInputStream(new FileInputStream(input)));
			DataOutputStream fout=new DataOutputStream(new BufferedOutputStream(new FileOutputStream(output)));
			HuffmanCoding hc=new HuffmanCoding();
			HuffmanNode hn=hc.createHuffmanTree(inputFrequencies(fin));
			hc.createCode(hn, 0, 0);
			outputChar(fin,fout,hn);
		}catch(IOException i){
			JOptionPane.showMessageDialog(null, "解压缩路径错误", "错误提示",JOptionPane.ERROR_MESSAGE);
		}
	}
	
}