同步阻塞式I/O(二)——基于字符的Writer、Reader

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不管是磁盘还是网络传输，最小的存储单元都是字节，而不是字符，所以 I/O 操作的都是字节而不是字符，但是为啥有操作字符的 I/O 接口呢？这是因为我们的程序中通常操作的数据都是以字符形式，有时我们必须把来自于"字节"层次结构中的类和“字符”层次结构中的类结合起来使用，为了实现这个目的，要用到"适配器"类：InputStreamReader可以把InputStream转化为Reader，而OutputStreamWriter可以把OutputStream转化为Writer。接着上一篇文章，本篇文章讲述同步并阻塞式线程的第二类，基于字符的Writer和Reader。

Writer相关类层次结构：

Reader相关类层次结构：

具体代码示例如下:

package io;import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.CharArrayReader;import java.io.CharArrayWriter;import java.io.FileReader;import java.io.FileWriter;import java.io.IOException;import java.io.PrintWriter;import java.io.StringReader;import java.io.StringWriter;public class ReaderandWriter {public static void main(String[] args) {/** * FileWriter与FileReader */try {FileWriter fw = new FileWriter("file.txt");String str = "大家好!";fw.write(str);fw.close();FileReader fr = new FileReader("file.txt");int ch = 0;while((ch = fr.read()) != -1){System.out.print((char)ch);}fr.close();} catch (IOException e) {e.printStackTrace();}/** * BufferedWriter与BufferedReader */try {BufferedWriter bw = new BufferedWriter( new FileWriter("file.txt"));String str = "你好!";bw.write(str);bw.close();BufferedReader br = new BufferedReader(new FileReader("file.txt"));System.out.println(br.readLine());br.close();} catch (IOException e) {e.printStackTrace();}/** * StringWriter与StringReader */try{String str = "今天很美好,明天很美好,后天还是很美好...";StringReader sr = new StringReader(str);String strRead = null;char[] size = new char[1024];while((sr.read(size)) != -1){strRead = new String(size);}sr.close();StringWriter sw = new StringWriter();sw.write(strRead);sw.close();System.out.println(sw.toString());}catch(Exception e){e.printStackTrace();}/** * PrintWriter */try {PrintWriter pw = new PrintWriter(new FileWriter("file.txt"));pw.append("你们好!");pw.close();BufferedReader br = new BufferedReader(new FileReader("file.txt"));System.out.println(br.readLine());br.close();} catch (IOException e) {e.printStackTrace();}/** * CahrArrayWriter与CharArrayReader */try {CharArrayWriter caw = new CharArrayWriter();String str = "我们都有一个家!";caw.write(str);caw.close();System.out.println(caw.toString());char[] chars = {'A','B','C','D','E'};CharArrayReader car = new CharArrayReader(chars);int len = 0;while((len = car.read()) != -1){System.out.print((char)len);}car.close();} catch (IOException e) {e.printStackTrace();}}}

图片来自:http://www.ibm.com/developerworks/cn/java/j-lo-javaio/

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