Java File compression and decompression (1)

Package com.cn; import java. io. file; import java. io. fileInputStream; import java. io. fileOutputStream; import java. io. inputStream; import java. util. enumeration; import java.util.zip. zipEntry; import java.util.zip. zipFile; import java.util.zip. zipOutputStream; // error Summary: // 1 about file. isFile () and file. isDirectory () memory deviation. // The error indicates that if Directory must be file, file is not necessarily Directory // correct: file and Directory are two different tasks. it can only be one of file or Directory. // 2 does not mean Execute a File f = new File ("F: \ x.txt"); // an x.txt File is generated on the hard drive. the following operations must be performed. // File f = new File ("F: \ x.txt"); // if (! F. exists () {// f. createNewFile (); //} // Where f. createNewFile () indicates that an empty File is created. // in most cases, File f = new File ("F: \ x.txt") is executed ") // use the input stream to reuse the output stream to operate the stream. For example, use the following example: // write hello world /// 3 to the x.txt file: // the zos stream is not disabled in the zip () method. an error occurred while extracting the compressed file. // Important Note: // 1. The core operation object for zip and unzip is every file !!! // For example, if you encounter a directory, it will traverse every file and compress it one by one. // do not mistakenly understand that a directory is compressed as a whole. // 2 in JAVA, each compressed file is represented by a ZipEntry. // You must obtain the complete path of each file during the compression process (from the outermost folder to the file itself) // use this full path to create a ZipEntry for each compressed file new () // 3 so zipEntry can be used to record the original directory hierarchy. decompress the package to keep it as it is. // you can also see that entrys is used during decompression. hasMoreElements (). // extract each zipEntry. // see the decompressed code: // perUnzipFilePath = unzipPath + zipEntry. getName (); public class TestZipAndUnZip {public static void main (Strin G [] args) throws Exception {TestZipAndUnZip test = new TestZipAndUnZip (); // compress and decompress a single file test.zip 2 ("F: \ kk \ cc.txt", "F: \ 11.zip"); test. unZipFile2 ("F :\\ 11.zip"," F :\\ test11 "); // compress and decompress a directory test.zip 2 (" F: \ kk "," F: \ 22.zip"); test. unZipFile2 ("F :\\ 22.zip"," F :\\ test22 ");} /*** this method compresses the file in a given path * @ param willZipPath path of the file to be compressed * @ param zipedPath the compressed path of the file */public void zip2 (String willZipPath, string zipedPath) {Try {File willZipFile = new File (willZipPath); File zipedFile = new File (zipedPath); ZipOutputStream zos = new ZipOutputStream (new FileOutputStream (zipedFile); if (willZipFile. isFile () {fileToZip2 (willZipPath, zos);} if (willZipFile. isDirectory () {dirToZip2 (willZipPath, willZipFile, zos);} // close the stream zos after the method is called. close ();} catch (Exception e) {}}/*** @ param willZipFilePath path of the file to be compressed * @ param zos compressed file output stream * 1 the following two statements of code * ZipEntry entry = new ZipEntry (); * zos. putNextEntry (entry); * Add the generated ZipEntry object to the compressed file * and then write the content to the compressed file to the ZipEntry object. close () but cannot zos here. close () * because the zos is passed in the previous method. the zos stream may be used again when the directory is compressed. if this is disabled, a File in the directory * is compressed */public void fileToZip2 (String willZipFilePath, ZipOutputStream zos) {try {File willZipFile = new File (willZipFilePath ); zipEntry entry = new ZipEntry (getEntryName2 (wil LZipFilePath, willZipFile); zos. putNextEntry (entry); FileInputStream FD = new FileInputStream (willZipFilePath); int len = 0; while (len = Fi. read ())! =-1) {zos. write (len);} FCM. close (); // stream close error! // Zos. close ();} catch (Exception e) {}}/*** @ param willZipDirctoryPath: Path of the original directory * @ param willZipedDirectory original directory * @ param zos compressed stream * Note: * when processing empty folders * getEntryName2 (willZipDirctoryPath, willZipedDirectory) + "/" * "is indispensable */public void dirToZip2 (String willZipDirctoryPath, File willZipedDirectory, zipOutputStream zos) {if (willZipedDirectory. isDirectory () {File [] files = willZipedDirectory. listFil Es (); // process empty folders if (files. length = 0) {ZipEntry zipEntry = new ZipEntry (getEntryName2 (willZipDirctoryPath, willZipedDirectory) + "/"); try {zos. putNextEntry (zipEntry);} catch (Exception e) {e. printStackTrace () ;}return ;}for (int I = 0; I <files. length; I ++) {File file = files [I]; // recursively call fileToZip () if (file. isFile () {fileToZip2 (file. getAbsolutePath (), zos);} // recursively call dirToZip () if (file. isDirectory () {DirToZip2 (file. getAbsolutePath (), file, zos );}}}} /*** @ param rawPath refers to the directory or full path of the file to be compressed * @ param file refers to the file or directory to be compressed * @ return entryName ** this method returns EntryName, indicates the complete path from the outermost directory to the file (directory) * remarks: * 1 all files in this example are stored in a disk, such as E: \ so rawPath. substring (3); * 2 comment on "@ param file files or directories to be compressed ". in most cases, * files are used, and only directories are empty folders. */public String getEntryName2 (String rawPath, File file) {try {String rawDir = rawPath. substring (3 ); Int rawDirIndex = file. getAbsolutePath (). indexOf (rawDir); String entryName = file. getAbsolutePath (). substring (rawDirIndex); return entryName;} catch (Exception e) {} return null ;} /*** @ param zipedFilePath: Path of the original compressed file * @ param unzipPath: Path of the decompressed file * Small sorting of file or directory operations: * 1 file the directory first. mkdir (s) () can * store files under it. for example, * File f = new File ("F: \ test \ x.txt"); if (! F. exists () f.createnewfile({{}}this is certainly an error because the directory of x.txt does not exist !! Therefore, it should be corrected to: File f = new File ("F: \ test \ x.txt"); f. getParentFile (). mkdirs (); if (! F. exists () {f. createNewFile ();} 2 Similarly, File f = new File ("F: \ test \ x.txt"); if (f. isFile () {System. out. println ("true");} else {System. out. println ("false");} the result is a problem similar to false3: File f = new File ("F: \ x.txt"); if (f. isFile () {System. out. println ("true");} else {System. out. println ("false");} The result is false because only a new File is created and not created !!! File f = new File ("F: \ x.txt"); f. createNewFile (); if (f. isFile () {System. out. println ("true");} else {System. out. println ("false");} is true here: if (zipEntry. isDirectory () {new File (perUnzipFilePath ). mkdirs ();} else {new File (perUnzipFilePath ). getParentFile (). mkdirs ();} has created each folder. then start streaming for each empty folder and each file. consistent with the above principle, I made a mistake at the beginning and did not use else {fos = new FileOutputStream (perUnzipFile); is = zipFile. getInputStream (zipEntr Y); while (len = is. read (buffer ))! =-1) {fos. write (buffer, 0, len) ;}} uses if (perUnzipFile. isFile () {}. Of course this is wrong. because this perUnzipFile does not execute perUnzipFile. createNewFile (); so it is not File. in a similar case, stream operations are mostly used for reading and writing. therefore, two operations related to File are summarized: 1 File f = new File (""); f. createNewFile (); then operate f 2 file f = new File (""); then use the input/output stream for stream operations. For example: File f = new File ("F: \ 2221x.txt "); FileOutputStream fos = new FileOutputStream (f); String string =" hello "; byte [] B = string. getBytes (); fos. write (B, 0, B. length); this example is correct. question: f. createNewFile () does not report an error. because the output stream FileOutputStream has already helped us do this. the modification example shows: File f = new File ("F: \ 2221x.txt"); if (f. isFile () {System. out. println ("true1");} else {System. out. println ("false1");} FileOutputStream fos = new FileOutputStream (f); if (f. isFile () {System. out. println ("true2");} else {System. out. println ("false2");} String string = "hello"; byte [] B = string. getBytes (); fos. writ E (B, 0, B. length); the output false1 and true2 are verified. */public void unZipFile2 (String zipedFilePath, String unzipPath) {FileOutputStream fos = null; InputStream is = null; ZipEntry zipEntry = null; String perUnzipFilePath = null; if (! UnzipPath. endsWith (File. separator) {unzipPath + = File. separator;} try {ZipFile zipFile = new ZipFile (zipedFilePath); Enumeration entries = zipFile. entries (); byte [] buffer = new byte [1024*8]; int len = 0; while (entries. hasMoreElements () {zipEntry = (ZipEntry) entries. nextElement (); perUnzipFilePath = unzipPath + zipEntry. getName (); // 1 create each folder if (zipEntry. isDirectory () {// process empty folders // create an empty directory new File (perUnzipFilePa Th ). mkdirs ();} else {// create its directory for each File new File (perUnzipFilePath ). getParentFile (). mkdirs ();} // 2. The operations in stream operations to process files in each folder // 2.1if are only performed for empty directories. therefore, the code in if can be commented out // without practical significance. // The operation in 2.2else is the stream operation File perUnzipFile = new File (perUnzipFilePath) for each specific File; if (perUnzipFile. isDirectory () {File [] files = perUnzipFile. listFiles (); for (int I = 0; I <files. length; I ++) {File file = files [I]; fos = new FileOutputStream (file ); Is = zipFile. getInputStream (zipEntry); while (len = is. read (buffer ))! =-1) {fos. write (buffer, 0, len) ;}} else {fos = new FileOutputStream (perUnzipFile); is = zipFile. getInputStream (zipEntry); while (len = is. read (buffer ))! =-1) {fos. write (buffer, 0, len) ;}} if (fos! = Null) {fos. close () ;}if (is! = Null) {is. close () ;}} catch (Exception e) {e. printStackTrace ();}}}

PS:

Java File compression and decompression (1), preferably.

Java File compression and decompression (3), followed.