java进行文件读写操作详解

直接上代码，有详细注释，有图解，相信你懂得！

package day14;



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() {

// D盘下有个Welcome.java文件，现在按字节读入：

int a = 0;

// int counter=0;

FileInputStream f11;

// 输入流

try {

f11 = new FileInputStream("D:" + s + "Welcome.java");

while ((a = f11.read()) != -1)

System.out.print((char) a); // 这里是按字节输出，中文字符无法正常输出，因为一个中文字符时两个字节。

System.out

.println("\n\n--------------------------------------------------\n");



FileReader f12 = new FileReader("D:" + s + "Welcome.java");

while ((a = f12.read()) != -1)

System.out.print((char) a);// 这里是按字符输出，中文字符都可以正常输出

System.out

.println("\n\n--------------------------------------------------\n");



f11.close();// 读完之后要关闭文件

f12.close();// 读完之后要关闭文件

} catch (FileNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}



private static void testOutput() {

// D盘下有个Welcome.java文件，现在按字节读入：

int a = 0;

// 输出流

File f21 = new File("D:" + s + "testFile" + s + "test1.txt");// 定义一个新的文件f21，然后判断在这一目录下是否存在，如果不存在，则创建之。

if (!f21.exists()) {

f21.getParentFile().mkdirs();

try {

f21.createNewFile();

// 将“Welcome.java”的内容复制到f21

FileOutputStream fos = new FileOutputStream(f21);

FileInputStream fis = new FileInputStream("D:" + s

+ "Welcome.java");// 读入“Welcome.java”文件

while ((a = fis.read()) != -1)

fos.write(a);// 将读入的内存写到fos中，现在得到的test1。txt就是复制Welcome。java的



// writer类

FileWriter f22 = new FileWriter("D:" + s + "testFile" + s

+ "test2.txt");

for (int i = 0; i < 65535; i++)

f22.write(i);// 将

// 写入到test2.txt中。由这里也可以看出，上面35-38行判断文件是否存在的语句也可以不要。

// 向文件中写入字符串

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() {

// D盘下有个Welcome.java文件，现在按字节读入：

int a = 0, counter = 0;

// 缓冲字符，实现高效写入

// BufferedWriter f31=new BufferedWriter(new

// FileWriter("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();// 刷新缓冲

f31.close();



BufferedReader f32 = new BufferedReader(new FileReader("D:" + s

+ "testFile" + s + "test4.txt"));

String s32;

System.out.println("输出文件f32的内容：");

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();

}

}



// 将压缩包zipfile解压到file中

public static void testZipToUnzip(ZipFile zipfile, File file) {

ZipEntry zentry = null;

File zipout;

InputStream zis = null;

FileOutputStream fos = null;

Enumeration e = zipfile.entries();// zipfile的目录



while (e.hasMoreElements()) {

zentry = (ZipEntry) e.nextElement();

System.out.println(zentry.getName());// zipfile下有哪些文件？可是为什么不按顺序输出？？



// 将解压后的文件放到file文件夹下：

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();

}

}