java 核心编程——IO流之字符流(三)

2017-09-13 12:26:18来源:cnblogs.com作者:柳暗花明睡一觉人点击

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1.字符流

  1.1 所有文件的存储都是字节的存储,我们日常在磁盘上保存的其实并不是文件的字符,而是先把字符转换成字节,再把这些字节储存到磁盘。在读取文件时,也是一个字节一个字节的读取,然后生成字节的序列。

  1.2 字节流可以处理任何对象,但是字符流呢,、只用来处理字符或者字符串。可以这样说,字节流呢,提供了最基本IO功能,可以处理任何IO操作,但是有一点,不可以直接处理Unicode字符,为什么呢,因为Unicode字符是一个单元为2个字节的字符,而字节流的处理单元为1个字节,字符流是由Java虚拟机将字节转化为2个字节的Unicode字符为单位的字符形成的。如果使用字节流直接处理Unicode字符的话,由于各种编码实现的不同,就很容易出现乱码。

  1.3实例上,我们日常处理的很多数据,都是文本,所以我们在字节流之外呢,又提出了字符流的概念,直接按照Java虚拟机的encode来处理,也就是在输出流和输入流之间 进行字符集的转换。

2.java字符流实现结构

  1.输入字符流

  2.输出字符流

  

3.字符流常用类

  3.1 字符数组输入输出流(CharArrayReader和CharArrayWriter)

package se.io;import com.sun.org.apache.xpath.internal.operations.String;import java.io.CharArrayReader;import java.io.CharArrayWriter;import java.io.IOException;public class CharArrayTest {    public static void main(String[] args) {        char[] chars = new char[3];        chars[0] = 100;        chars[1] = 101;        chars[2] = 102;        CharArrayReader charArrayReader = new CharArrayReader(chars);        try {            char[] buf = new char[1024];            charArrayReader.read(buf);            CharArrayWriter charArrayWriter = new CharArrayWriter();            charArrayWriter.write(buf);            System.out.println(charArrayWriter.toString());            charArrayWriter.close();            charArrayReader.close();        } catch (IOException e) {            e.printStackTrace();        }    }}

  3.2文件输入输出流(FileWriter和FileReader)

package se.io;import java.io.FileNotFoundException;import java.io.FileReader;import java.io.FileWriter;import java.io.IOException;public class FileCharTest {    public static void main(String[] args) {        try {            FileReader fileReader = new FileReader("E://test//data.txt");            char[] chars = new char[1024];            int i = fileReader.read(chars);            FileWriter fileWriter = new FileWriter("E://test//filewriter.txt");            fileWriter.write(chars,0,i);            fileWriter.close();            fileReader.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }}

  3.3管道输入输出流(PipedReader 和 PipedWriter)

package se.io;import java.io.IOException;import java.io.PipedReader;import java.io.PipedWriter;public class PipedChar {    public static void main(String[] args) {        SenderChar senderChar = new SenderChar();        PipedWriter pipedWriter = senderChar.getWriter();        ReceiverChar receiverChar = new ReceiverChar();        PipedReader pipedReader =receiverChar.getReader();        try {            pipedWriter.connect(pipedReader);            senderChar.start();            receiverChar.start();        } catch (IOException e) {            e.printStackTrace();        }    }}//创建发送者类class SenderChar extends Thread{    private PipedWriter writer = new PipedWriter();    public PipedWriter getWriter() {        return writer;    }    public void run(){        String s = new String("hello,world");        try {            writer.write(s);            writer.close();        } catch (IOException e) {            e.printStackTrace();        }    }}//创建接受者class ReceiverChar extends  Thread{    private PipedReader reader = new PipedReader();    public PipedReader getReader() {        return reader;    }    public  void run(){        String s= null;        char[] chars = new char[1024];        try {            int i = reader.read(chars);            s = new String(chars,0,i);            System.out.println(s);            reader.close();        } catch (IOException e) {            e.printStackTrace();        }    }}

  3.4缓存输入输出流(BufferedReader 和BufferedWriter)

package se.io;import java.io.*;public class BufferWriterTest {    public static void main(String[] args) {        try {            //构建文件输入输出字符流,如果指定文件不存在,则自动生成。            FileReader fileReader = new FileReader("E://test//data.txt");            FileWriter  fileWriter = new FileWriter("E://test//data2.txt");            //构建过滤缓存流            BufferedReader bufferedReader = new BufferedReader(fileReader);            BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);            //缓存数组            char[] chars = new char[1024];            int offset = 0 ;            //读取字符            while(bufferedReader.ready()) {                offset = bufferedReader.read(chars);            }            //输出字符            bufferedWriter.write(chars,0,offset);            //关闭流            bufferedWriter.close();            bufferedReader.close();        } catch (IOException e) {            e.printStackTrace();        }    }}

   3.5格式化输出流(PrinterWriter)

package se.io;import java.io.FileWriter;import java.io.FilterWriter;import java.io.IOException;import java.io.PrintWriter;import java.util.Date;public class PrintWriterTest {    public static void main(String[] args) {        try {            //创建文件输出流            FileWriter fileWriter = new FileWriter("E://test//data3.txt");            //创建格式化对象输出流            PrintWriter printWriter = new PrintWriter(fileWriter);            //写入数据            printWriter.printf("%1$tY年%1$tm月%1$td日", new Date());            printWriter.print(123);            printWriter.print(12.32);            //关闭流            printWriter.close();        } catch (IOException e) {            e.printStackTrace();        }    }}

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