gzip Java 使用 GZIP 进行压缩和解压缩详解编程语言

CompressFileGZIP.java

import java.util.zip.GZIPOutputStream; 
import java.io.FileOutputStream; 
import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import java.io.IOException; 
 
/** 
 * ----------------------------------------------------------------------------- 
 * Used to provide an example of compressing a file using the GZIP Format. 
 * 
 * @version 1.0 
 * @author  Jeffrey M. Hunter  ([email protected]) 
 * @author  http://www.idevelopment.info 
 * ----------------------------------------------------------------------------- 
 */ 
 
public class CompressFileGZIP { 
 
    /** 
     * Perform file compression. 
     * @param inFileName Name of the file to be compressed 
     */ 
    private static void doCompressFile(String inFileName) { 
 
        try { 
 
            System.out.println("Creating the GZIP output stream."); 
            String outFileName = inFileName + ".gz"; 
            GZIPOutputStream out = null; 
            try { 
                out = new GZIPOutputStream(new FileOutputStream(outFileName)); 
            } catch(FileNotFoundException e) { 
                System.err.println("Could not create file: " + outFileName); 
                System.exit(1); 
            } 
 
            System.out.println("Opening the input file."); 
            FileInputStream in = null; 
            try { 
                in = new FileInputStream(inFileName); 
            } catch (FileNotFoundException e) { 
                System.err.println("File not found. " + inFileName); 
                System.exit(1); 
            } 
 
            System.out.println("Transfering bytes from input file to GZIP Format."); 
            byte[] buf = new byte[1024]; 
            int len; 
            while((len = in.read(buf)) > 0) { 
                out.write(buf, 0, len); 
            } 
            in.close(); 
 
            System.out.println("Completing the GZIP file"); 
            out.finish(); 
            out.close(); 
 
        } catch (IOException e) { 
            e.printStackTrace(); 
            System.exit(1); 
        } 
 
    } 
 
    /** 
     * Sole entry point to the class and application. 
     * @param args Array of String arguments. 
     */ 
    public static void main(String[] args) { 
 
        if (args.length != 1) { 
            System.err.println("Usage: java CompressFileGZIP filename"); 
        } else { 
            doCompressFile(args[0]); 
        } 
 
    } 
 
}

UncompressFileGZIP.java

import java.util.zip.GZIPInputStream; 
import java.io.FileOutputStream; 
import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import java.io.IOException; 
 
/** 
 * ----------------------------------------------------------------------------- 
 * Used to provide an example of uncompressing a file in the GZIP Format. 
 * 
 * @version 1.0 
 * @author  Jeffrey M. Hunter  ([email protected]) 
 * @author  http://www.idevelopment.info 
 * ----------------------------------------------------------------------------- 
 */ 
 
public class UncompressFileGZIP { 
 
    /** 
     * Uncompress the incoming file. 
     * @param inFileName Name of the file to be uncompressed 
     */ 
    private static void doUncompressFile(String inFileName) { 
 
        try { 
 
            if (!getExtension(inFileName).equalsIgnoreCase("gz")) { 
                System.err.println("File name must have extension of /".gz/""); 
                System.exit(1); 
            } 
 
            System.out.println("Opening the compressed file."); 
            GZIPInputStream in = null; 
            try { 
                in = new GZIPInputStream(new FileInputStream(inFileName)); 
            } catch(FileNotFoundException e) { 
                System.err.println("File not found. " + inFileName); 
                System.exit(1); 
            } 
 
            System.out.println("Open the output file."); 
            String outFileName = getFileName(inFileName); 
            FileOutputStream out = null; 
            try { 
                out = new FileOutputStream(outFileName); 
            } catch (FileNotFoundException e) { 
                System.err.println("Could not write to file. " + outFileName); 
                System.exit(1); 
            } 
 
            System.out.println("Transfering bytes from compressed file to the output file."); 
            byte[] buf = new byte[1024]; 
            int len; 
            while((len = in.read(buf)) > 0) { 
                out.write(buf, 0, len); 
            } 
 
            System.out.println("Closing the file and stream"); 
            in.close(); 
            out.close(); 
 
        } catch (IOException e) { 
            e.printStackTrace(); 
            System.exit(1); 
        } 
 
    } 
 
    /** 
     * Used to extract and return the extension of a given file. 
     * @param f Incoming file to get the extension of 
     * @return <code>String</code> representing the extension of the incoming 
     *         file. 
     */  
    public static String getExtension(String f) { 
        String ext = ""; 
        int i = f.lastIndexOf('.'); 
 
        if (i > 0 &&  i < f.length() - 1) { 
            ext = f.substring(i+1); 
        }        
        return ext; 
    } 
 
    /** 
     * Used to extract the filename without its extension. 
     * @param f Incoming file to get the filename 
     * @return <code>String</code> representing the filename without its 
     *         extension. 
     */  
    public static String getFileName(String f) { 
        String fname = ""; 
        int i = f.lastIndexOf('.'); 
 
        if (i > 0 &&  i < f.length() - 1) { 
            fname = f.substring(0,i); 
        }        
        return fname; 
    } 
 
    /** 
     * Sole entry point to the class and application. 
     * @param args Array of String arguments. 
     */ 
    public static void main(String[] args) { 
 
        if (args.length != 1) { 
            System.err.println("Usage: java UncompressFileGZIP gzipfile"); 
        } else { 
            doUncompressFile(args[0]); 
        } 
 
    } 
 
}