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java温故而知新（6）深入理解IO Stream
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一、什么是IO StreamStream 是在编程语言中对输入输出的总称 （一种比喻的称谓。Stream 为流水，输入输出实际上就是指数据的流动，数据由一个地方运动的另一个地方，就像流水一样，程序员将输入输出比作流水，再恰当不过了)。 流按照其所载内容分类，大致可分为字节流和字符流两大类。1、字节流 （Byte Stream）在计算机中，byte是相当于机器语言中的单词，他在Java中统一由InputStream和OutputStream作处理。 2、字符流（Character Stream）而在编码体系中，一般采用Char（2 bytes）, 他在Java中统一由Reader和Writer作处理。 InputStream, OutputStream, Reader和Writer, 作为在java.io.*包的顶级父类，定义了IO Process中最抽象的处理和规范。对于实际的应用，他们并不适用。于是根据各种实际的需要，由他们派生出来形式各样各具特色的子类。 二、IO Stream分类1 Node Stream :基本流，可以从名称中看出他是从哪个地方输入输出的。1.1 用于文件输入输出流： FileInputStream, FileOutputStream1.2 用于内存数组的输入输出流：ByteArrayInputStream, ByteArrayOutputStream1.3 用于字符串的输入输出流：StringArrayInputStream, StringArrayOutputStream1.4 用于管道的输入输出流：PipedInputStream, PipeOutStream (用于线程间的交互)….2 Processing Stream: 处理流，是对Node Stream的加强和补充，可以看作是高级流。 要构造一个高级流通常要以一个基础流为基础（如通过构造函数的参数传入）2.1 用于提高输入输出效率的缓冲流：BufferedInputStream, BufferedOutputStream2.2 用于数据转化的数据流： DataInputStream (用于读取Java的Primitive Data Type) , DataOutputStream2.3 8位转化为16位的流： InputStreamReader, OutputWriter (用于沟通byte 和Char )2.4 打印流： PintStream….三、IO 编程的一般流程
1. 创建基本流2. 升级基本流到高级流3. 使用在高级流中的方法作读写操作4. 关闭流并释放资源-------------------------------------------------------------------------------
1. Creat node stream;
2. Upgrade node stream to processing stream if necessary
3. Use the methods in the stream object to read or write
4. Close the stream and release the resource
------------------------------------------------------------------------------
1. Create InputStream/Reader
2. Upgrade to Buffered
3. Use readLine()
While((str=in.readln())!=null)
4. close()
------------------------------------------------------------------------------
1. Create OutputStream/Writer
2. Upgrade to PrintWriter
3. Use println()
4. close()
四、经典IO实例import java.io.*;
/*
1. Creat node stream;
2. Upgrade node stream to processing stream if necessary
3. Use the methods in the stream object to read or write
4. Close the stream and release the resource
--------------------------------------------------------
1. Create InputStream/Reader
2. Upgrade to Buffered
3. Use readLine()
While((str=in.readln())!=null)
4. close()
--------------------------------------------------------
1. Create OutputStream/Writer
2. Upgrade to PrintWriter
3. Use println()
4. close()
*/
public class IOProcessSample{ public static void main(String[] args) {
//Create a file based on the first command-line argument to the program
File file= new File(args[0]);
//Create buffered reader from the standard input
BufferedReader in=new BufferedReader(new InputStreamReader(System.in)); System.out.println("Press ctr-d or ctr-z to end");
String str;
try{
//Create a print write to write on a file
//PrintWriter is required to handled the IO exception
PrintWriter out= new PrintWriter(file);
//Read from the standard input and write to the file
while((str=in.readLine())!=null){
out.println(str);
}
//close the stream and release the resource
in.close();
out.close();
}
catch(FileNotFoundException e){
System.err.println("File not found in part 1 : "+file);
}
catch (IOException e){
e.printStackTrace();
}
finally{
System.out.println("-----------Part1 is ended-----------------------");
}
//////////////////////////////////////////////////////////////////////////////
try{
//Create a buffer reader from a file
in=new BufferedReader(new FileReader(file));
//Read the file and print the content on the screen.
while((str=in.readLine())!=null){
System.out.println(str);
}
//close the stream and release the resource
in.close();
}
catch (FileNotFoundException e){
System.err.println("File not found in part 2: "+file);
}
catch (IOException e){
e.printStackTrace();
}
finally{
System.out.println("----------------------The End -------------------------");
}
}
}
1 Node Stream :基本流，可以从名称中看出他是从哪个地方输入输出的。
1.1 用于文件输入输出流： FileInputStream, FileOutputStream
1.2 用于内存数组的输入输出流：ByteArrayInputStream, ByteArrayOutputStream
1.3 用于字符串的输入输出流：StringArrayInputStream, StringArrayOutputStream
1.4 用于管道的输入输出流：PipedInputStream, PipeOutStream (用于线程间的交互)
….
2 Processing Stream: 处理流，是对Node Stream的加强和补充，可以看作是高级流。 要构造一个高级流通常要以一个基础流为基础（如通过构造函数的参数传入）
2.1 用于提高输入输出效率的缓冲流：BufferedInputStream, BufferedOutputStream
2.2 用于数据转化的数据流： DataInputStream (用于读取Java的Primitive Data Type) , DataOutputStream
2.3 8位转化为16位的流： InputStreamReader, OutputWriter (用于沟通byte 和Char )
2.4 打印流： PintStream
….
三、IO 编程的一般流程
1. 创建基本流
2. 升级基本流到高级流
3. 使用在高级流中的方法作读写操作
4. 关闭流并释放资源
-------------------------------------------------------------------------------
1. Creat node stream;
2. Upgrade node stream to processing stream if necessary
3. Use the methods in the stream object to read or write
4. Close the stream and release the resource
------------------------------------------------------------------------------
1. Create InputStream/Reader
2. Upgrade to Buffered
3. Use readLine()
While((str=in.readln())!=null)
4. close()
------------------------------------------------------------------------------
1. Create OutputStream/Writer
2. Upgrade to PrintWriter
3. Use println()
4. close()
四、经典IO实例import java.io.*;
/*
1. Creat node stream;
2. Upgrade node stream to processing stream if necessary
3. Use the methods in the stream object to read or write
4. Close the stream and release the resource
--------------------------------------------------------
1. Create InputStream/Reader
2. Upgrade to Buffered
3. Use readLine()
While((str=in.readln())!=null)
4. close()
--------------------------------------------------------
1. Create OutputStream/Writer
2. Upgrade to PrintWriter
3. Use println()
4. close()
*/
public class IOProcessSample{ public static void main(String[] args) {
//Create a file based on the first command-line argument to the program
File file= new File(args[0]);
//Create buffered reader from the standard input
BufferedReader in=new BufferedReader(new InputStreamReader(System.in)); System.out.println("Press ctr-d or ctr-z to end");
String str;
try{
//Create a print write to write on a file
//PrintWriter is required to handled the IO exception
PrintWriter out= new PrintWriter(file);
//Read from the standard input and write to the file
while((str=in.readLine())!=null){
out.println(str);
}
//close the stream and release the resource
in.close();
out.close();
}
catch(FileNotFoundException e){
System.err.println("File not found in part 1 : "+file);
}
catch (IOException e){
e.printStackTrace();
}
finally{
System.out.println("-----------Part1 is ended-----------------------");
}
//////////////////////////////////////////////////////////////////////////////
try{
//Create a buffer reader from a file
in=new BufferedReader(new FileReader(file));
//Read the file and print the content on the screen.
while((str=in.readLine())!=null){
System.out.println(str);
}
//close the stream and release the resource
in.close();
}
catch (FileNotFoundException e){
System.err.println("File not found in part 2: "+file);
}
catch (IOException e){
e.printStackTrace();
}
finally{
System.out.println("----------------------The End -------------------------");
}
}
}
import java.io.*;
/*
1. Creat node stream;
2. Upgrade node stream to processing stream if necessary
3. Use the methods in the stream object to read or write
4. Close the stream and release the resource
--------------------------------------------------------
1. Create InputStream/Reader
2. Upgrade to Buffered
3. Use readLine()
While((str=in.readln())!=null)
4. close()
--------------------------------------------------------
1. Create OutputStream/Writer
2. Upgrade to PrintWriter
3. Use println()
4. close()
*/
public class IOProcessSample{ public static void main(String[] args) {
//Create a file based on the first command-line argument to the program
File file= new File(args[0]);
//Create buffered reader from the standard input
BufferedReader in=new BufferedReader(new InputStreamReader(System.in)); System.out.println("Press ctr-d or ctr-z to end");
String str;
try{
//Create a print write to write on a file
//PrintWriter is required to handled the IO exception
PrintWriter out= new PrintWriter(file);
//Read from the standard input and write to the file
while((str=in.readLine())!=null){
out.println(str);
}
//close the stream and release the resource
in.close();
out.close();
}
catch(FileNotFoundException e){
System.err.println("File not found in part 1 : "+file);
}
catch (IOException e){
e.printStackTrace();
}
finally{
System.out.println("-----------Part1 is ended-----------------------");
}
//////////////////////////////////////////////////////////////////////////////
try{
//Create a buffer reader from a file
in=new BufferedReader(new FileReader(file));
//Read the file and print the content on the screen.
while((str=in.readLine())!=null){
System.out.println(str);
}
//close the stream and release the resource
in.close();
}
catch (FileNotFoundException e){
System.err.println("File not found in part 2: "+file);
}
catch (IOException e){
e.printStackTrace();
}
finally{
System.out.println("----------------------The End -------------------------");
}
}
}
