Java 實現壓縮檔

Java comes with “java.util.zip” library to implement the data compression in ZIp format. The overall concept is quite straightforward.

·Read file with “FileInputStream”
·Add the file name to “ZipEntry” and output it to “ZipOutputStream“

Simple ZIP example

Read a file “C:\\user.txt” and compress it into a zip file – “C:\\user.zip“.

    package org.hello.zip;    import java.io.FileInputStream;    import java.io.FileOutputStream;    import java.io.IOException;    import java.util.zip.ZipEntry;    import java.util.zip.ZipOutputStream;    public class JavaZip {        public static void main(String[] args) {            byte[] buffer = new byte[1024];            try {                FileOutputStream fos = new FileOutputStream("C:\\user.zip");                ZipOutputStream zos = new ZipOutputStream(fos);                ZipEntry ze = new ZipEntry("user.txt");                zos.putNextEntry(ze);                FileInputStream in = new FileInputStream("C:\\user.txt");                /*                 * int java.io.FileInputStream.read(byte[] b) throws IOException                 * Reads up to b.length bytes of data from this input stream into an                 * array of bytes. This method blocks until some input is available.                 * Overrides: read(...) in InputStream Parameters: b the buffer into                 * which the data is read. Returns: the total number of bytes read                 * into the buffer, or -1 if there is no more data because the end                 * of the file has been reached.                 */                int len;                while ((len = in.read(buffer)) > 0) {                    zos.write(buffer, 0, len);                }                in.close();                zos.closeEntry();                zos.close();                System.out.println("Compress Completed!");            } catch (IOException e) {                e.printStackTrace();            }        }    }

Advance ZIP example – Recursively

Read all files from folder “C:\\Logs” and compress it into a zip file – “C:\\Logs.zip“. It will recursively zip a directory as well.

    package org.hello.zip;    import java.io.File;    import java.io.FileInputStream;    import java.io.FileOutputStream;    import java.io.IOException;    import java.util.ArrayList;    import java.util.List;    import java.util.zip.ZipEntry;    import java.util.zip.ZipOutputStream;    public class AppZip {        List<String> fileList;        private static final String OUTPUT_ZIP_FILE = "C:\\Logs.zip";        private static final String SOURCE_FOLDER = "C:\\Logs";                AppZip(){            fileList =new ArrayList<String>();        }                public static void main(String[] args){            AppZip appzip = new AppZip();            appzip.generateFileList(new File(SOURCE_FOLDER));            appzip.zipIt(OUTPUT_ZIP_FILE);        }        private void zipIt(String zipFile) {            byte[] buffer = new byte[1024];            try{                FileOutputStream fos = new FileOutputStream(zipFile);                ZipOutputStream zos = new ZipOutputStream(fos);                System.out.println("Output to Zip: "+ zipFile);                for(String filename :this.fileList){                    System.out.println("File added: "+filename);                    ZipEntry ze = new ZipEntry(filename);                    zos.putNextEntry(ze);                                        FileInputStream in = new FileInputStream(SOURCE_FOLDER + File.separator + filename);                                        int len;                    while((len = in.read(buffer)) > 0){                        zos.write(buffer,0,len);                    }                    in.close();                }                zos.closeEntry();                zos.close();                System.out.println("Compress Completed.");                            }catch(IOException e){                e.printStackTrace();            }                    }        /**         * Traverse a directory and get all files,         * and add the file into fileList         * @param node file or directory         */        private void generateFileList(File node) {            //add file only            if(node.isFile()){                fileList.add(generateZipEntry(node.getAbsoluteFile().toString()));            }                    if(node.isDirectory()){                String[] subNote = node.list();                for(String filename : subNote){                    generateFileList(new File(node, filename));                }            }                }         /**         * Format the file path for zip         * @param file file path         * @return Formatted file path         */        private String generateZipEntry(String filename) {            return filename.substring(SOURCE_FOLDER.length()+1, filename.length());        }    }