黑马程序员 java基础之IO流（一）

使用IO流的规律：

1、首先知道IO流的体系，分为输入和输出流，输入流:InputStream,Reader.输出流：OutputStream，Writer

2、明确源和目的，源 需要用到InputStream或者Reader；

目的需要用到OutputSteam或者Writer；

3、明确具体文件类型：如果是文本文件，用字符流Reader/Writer；

如果是非文本文件，如图片，视频等，用字节流InputStream/OutputStream；

4、通过设备确定用哪个具体对象：源分为：内存，硬盘，键盘。

目的分为：内存，硬盘，控制台。

5、是否需要提高效率：BufferedReader/Writer

练习一：读取一个.java文件，打印出来

class IOStream{

public static void main(String [] args){

FileReader fr = null;

try{

fr = new FileReader("area.java");

char [] ch = new char[1024];

int num = 0;

while((num = fr.read(ch))!=-1){

System.out.print("area.java:" + new String(ch,0,num));

}

}

catch(IOException e){

System.out.println(e.toString());

}

finally{

try{

fr.close();

}

catch(IOException e){

System.out.println(e.toString());

}

}

}

}

练习二：将一个c盘的文件复制到d盘

class IOStream{

public static void main(String [] args){

FileWriter fw = null;

FileReader fr = null;

try{

fw = new FileWriter("D:\\area.java");

fr = new FileReader("area.java");

char [] ch = new char[1024];

int num = 0;

while((num = fr.read(ch))!=-1){

fw.write(ch,0,num);

}

}

catch(IOException e){

System.out.println(e.toString());

}

finally{

if(fr == null)

try{

fr.close();

}

catch(IOException e){

System.out.println(e.toString());

}

if(fw == null)

try{

fw.close();

}

catch(IOException e){

System.out.println(e.toString());

}

}

}

}

练习三：练习二的改进版，利用缓冲区复制文本

class IOStream{

public static void main(String [] args){

BufferedReader br = null;

BufferedWriter bw = null;

try{

br = new BufferedReader(new FileReader("area.java"));

bw = new BufferedWriter(new FileWriter("D:\\area.java"));

String s = null;

while((s = br.readLine())!=null){

bw.write(s);

bw.newLine();

bw.flush();

}

}

catch(IOException e){

System.out.println(e.toString());

}

finally{

if(bw==null)

try{

bw.close();

}

catch(IOException e){

System.out.println(e.toString());

}

if(br==null)

try{

br.close();

}

catch(IOException e){

System.out.println(e.toString());

}

}

}

}

练习四：拷贝一张图片

class IOStream{

public static void main(String [] args){

FileInputStream fis = null;

FileOutputStream fos = null;

try{

fis = new FileInputStream("34.jpg");

fos = new FileOutputStream("D:\\background.jpg");

byte [] bt = new byte[1024];

int num = 0;

while((num = fis.read(bt))!=-1){

fos.write(bt);

}

}

catch(IOException e){

System.out.println(e.toString());

}

finally{

if(fis==null)

try{

fis.close();

}

catch(IOException e){

System.out.println(e.toString());

}

if(fos==null)

try{

fos.close();

}

catch(IOException e){

System.out.println(e.toString());

}

}

}

}