This article describes how Java implements file reading, writing and compression through examples. The specific code is as follows:
package com.toone.iform.action.common;import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io .FileOutputStream; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.io.InputStream; import java.util.Enumeration; import java.util.Random; import java.util.zip.ZipEntry; import java.util.zip.ZipException; import java.util. zip.ZipFile; public class TestFileIO { static String s = File.separator; private static void testInput() { // There is a Welcome.java file under the D drive. Now read it in by bytes: int a = 0; // int counter=0; FileInputStream f11; // Input stream try { f11 = new FileInputStream("D:" + s + "Welcome.java"); while ((a = f11.read()) != -1) System.out.print((char) a); // The output here is by byte. Chinese characters cannot be output normally because one Chinese character is two bytes. System.out.println("/n/n--------------------------------------- -----------/n"); FileReader f12 = new FileReader("D:" + s + "Welcome.java"); while ((a = f12.read()) != - 1) System.out.print((char) a);// Here is the output by character, Chinese characters can be output normally System.out.println("/n/n-------------------------- -----------------------/n"); f11.close();// Close the file after reading f12.close();// Close the file after reading} catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } private static void testOutput() { // There is a Welcome.java file under the D drive. Now read it in by bytes: int a = 0; // Output stream File f21 = new File ("D:" + s + "testFile" + s + "test1.txt"); // Define a new file f21, and then determine whether it exists in this directory. If it does not exist, create it. if (!f21.exists()) { f21.getParentFile().mkdirs(); try { f21.createNewFile(); // Copy the contents of "Welcome.java" to f21 FileOutputStream fos = new FileOutputStream(f21); FileInputStream fis = new FileInputStream("D:" + s + "Welcome.java");// Read the "Welcome.java" file while ((a = fis.read()) != -1) fos.write(a);// Write the read memory to fos, and now the test1.txt is Copy the // writer class FileWriter of Welcome.java f22 = new FileWriter("D:" + s + "testFile" + s + "test2.txt"); for (int i = 0; i < 65535; i++) f22.write(i);//Write to test2.txt. It can also be seen from here that the statements in lines 35-38 above to determine whether the file exists can be omitted. // Write a string to the file FileWriter f23 = new FileWriter("D:" + s + "testFile" + s + "test3.txt"); f23.write("Hello, world!"); fos.close (); fis.close(); f22.close(); f23.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } private static void testBufferring() { // There is a Welcome.java file under the D drive, now read it in by bytes: int a = 0, counter = 0; // Buffer characters, implementation Efficient writing // BufferedWriter f31=new BufferedWriter(newFileWriter("D"+s+"testFile"+s+"test4.txt")); BufferedWriter f31; try { f31 = new BufferedWriter(new FileWriter("D:" + s + "testFile" + s + "test4.txt")); for (int i = 1; i <= 100; i++) { f31 .write(String.valueOf(new Random().nextInt(100)) + " "); if (i % 10 == 0) f31.newLine(); } f31.flush();// Refresh buffer f31.close(); BufferedReader f32 = new BufferedReader(new FileReader("D:" + s + "testFile" + s + "test4.txt")); String s32; System.out.println("Contents of output file f32:"); while ((s32 = f32.readLine()) != null) System.out.println(s32); f32.close(); System.out.println("/n----------- ---------------------------------------/n"); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } private static void testZip() { try { File f1 = new File("D:/test.zip"); File f2 = new File("D:/testFile/testzip"); ZipFile zf = new ZipFile(f1); testZipToUnzip(zf, f2); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } // Extract the compressed package zipfile into file public static void testZipToUnzip(ZipFile zipfile, File file) { ZipEntry zentry = null; File zipout; InputStream zis = null; FileOutputStream fos = null; Enumeration e = zipfile.entries();// The directory of the zipfile while (e.hasMoreElements()) { zentry = (ZipEntry) e.nextElement(); System.out.println(zentry.getName());//What files are under zipfile? But why is it not output in order? ? //Put the decompressed file into the file folder: zipout = new File(file + s + zentry.getName()); if (!zentry.isDirectory()) { try { zis = zipfile.getInputStream(zentry) ; if (!zipout.exists()) zipout.getParentFile().mkdirs(); fos = new FileOutputStream(zipout); byte[] b = new byte[1024]; int length; while ((length = zis.read(b)) > 0) { fos.write(b, 0, length); } fos.close(); zis.close(); } catch (ZipException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } catch (IOException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } } } } public static void main(String[] args) throws ZipException { // TODO Auto-generated method stub testInput(); testOutput(); testBufferring(); testZip(); }}