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();
}
}