java笔记八：IO流之字符流与字符缓冲流

java中字符流主要都是继承于Reader和Writer两个抽象类。用于对字符文本的读写操作。

 

一、转换类流

 1 package com.iotest;

 3 import java.io.FileInputStream;

 4 import java.io.FileNotFoundException;

 5 import java.io.FileOutputStream;

 6 import java.io.IOException;

 7 import java.io.InputStreamReader;

 8 import java.io.OutputStreamWriter;

10 public class ConverseStreamDemo {

12 public static void main(String[] args) {

13 String s = “F:\shar\test\test3.txt”;

14 try {

15 //将字节流转为字符流

16 OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(s));

17 osw.write(“中国北京”);

18 System.out.println(osw.getEncoding());

19 osw.close();

20 osw = new OutputStreamWriter(new FileOutputStream(s,true),”GB2312”);

21 osw.write(“中国北京”);

22 System.out.println(osw.getEncoding());

23 osw.close();

24 } catch (FileNotFoundException e) {

25 // TODO Auto-generated catch block

26 e.printStackTrace();

27 } catch (IOException e) {

28 // TODO Auto-generated catch block

29 e.printStackTrace();

31 try {

32 //将字节流转为字符流

33 InputStreamReader isr = new InputStreamReader(new FileInputStream(s),”GB2312”);

34 int c;

35 while((c=isr.read()) != -1){

36 System.out.print((char)c);

38 System.out.println();

39 isr.close();

40 } catch (FileNotFoundException e) {

41 // TODO Auto-generated catch block

42 e.printStackTrace();

43 } catch (IOException e) {

44 // TODO Auto-generated catch block

45 e.printStackTrace();

49 }

 

二、FileReader和FileWriter

 1 package com.iotest;

 3 import java.io.FileNotFoundException;

 4 import java.io.FileReader;

 5 import java.io.FileWriter;

 6 import java.io.IOException;

 8 使用flush（）将流数据刷到目标里，这时流还存活着，还可以继续使用该流进行别的操作。

 9 close（）虽然也有flush（）的效果但是这时流已经死了，你如果想继续使用流的话就必须在此建立流

11 public class MutiplicationTable {

13 public static void main(String[] args) throws IOException {

14 String s = “F:\shar\test\test5.txt”;

15 FileWriter fw = new FileWriter(s);

16 FileReader fr = new FileReader(s);

17 for (int i = 1; i i++) {

18 for (int j = 1; j j++) {

19 String str = i + ““ + j + “=” + ij + “ “;

20 fw.write(str);

22 fw.write(“\r\n”);

23 /flush是指强行将输出流中的数据写到文件里面去。如果写到这里的话就是一行一行的写入文件

24 最好每写完一部分就刷新一次，如果最后刷新的话可能会造成数据的丢失

25 */

26 fw.flush();

28 //如果又不写flush()又不写close()，则不会写入任何内容到文本里。只是写到了缓冲区

29 //fw.flush(); 写到这里的话就是所有的内容一起写进文件

30 //fw.close(); close之前会调用flush()

31 //读字符输入流的数据

32 int c;

33 while ((c=fr.read())!=-1) {

34 System.out.print((char)c);

38 }

 

三、BufferedReader和BufferedWriter

 1 package com.iotest;

 3 import java.io.BufferedOutputStream;

 4 import java.io.BufferedWriter;

 5 import java.io.FileOutputStream;

 6 import java.io.FileWriter;

 7 import java.io.IOException;

 9 public class PrimeNumber {

10 BufferedWriter bw = null;

11 String fileName = “F:\shar\test\test7.txt”;

12 //判断是否是质数

13 public boolean isPrime(int n){

14 for(int i=2;i =n/2;i++){

15 if(n%i == 0){

16 return false;

19 return true;

21 void printPrime(int m) throws IOException{

22 //将字节流转缓冲流

23 bw = new BufferedWriter(new FileWriter(fileName));

24 int j = 0;

25 for (int i = 2; i i++) {

26 if(isPrime(i)){

27 j++;

28 String s = String.valueOf(i);

29 String s1 = s + “ “;

30 bw.write(s1); //写入文本文件

31 if(j==10){

32 j = 0;

33 bw.newLine(); //写入一个行分隔符

34 bw.flush(); //强制刷新

39 bw.close();

41 public static void main(String[] args) throws IOException {

42 PrimeNumber pn = new PrimeNumber();

43 pn.printPrime(100);

46 }

四、PrintWriter

 1 package com.iotest;

 3 import java.io.FileWriter;

 4 import java.io.IOException;

 5 import java.io.PrintWriter;

 7 public class PrintWriterDemo {

 9 public static void main(String[] args) throws IOException {

10 int A = 0; //千位

11 int B = 0; //百位

12 int C = 0; //十位

13 int num = 0;

14 String fileName = “F:\shar\test\test8.txt”;

15 FileWriter fw = new FileWriter(fileName); //字符输出流

16 PrintWriter pw = new PrintWriter(fw); //将字节输出流转为PrintWriter

17 for (int i = 1000; i 10000; i++) {

18 A = i/1000;

19 B = i/100 % 10;

20 C = i/10 % 10;

21 if(i%11==0 A == B+C){

22 pw.print(i+” “);

23 if(++num % 7 == 0){

24 pw.println(); //写入回车换行

25 pw.flush(); //强制刷新流

29 fw.close();

33 }

五、标准IO

 1 package com.iotest;

 3 import java.io.BufferedReader;

 4 import java.io.FileWriter;

 5 import java.io.IOException;

 6 import java.io.InputStreamReader;

 7 import java.io.PrintWriter;

 8 import java.util.Scanner;

10 public class PackStardIO {

12 public static void main(String[] args) throws IOException {

13 BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

14 PrintWriter o = new PrintWriter(System.out); //包装标准输出

15 String s;

16 while((s=br.readLine())!=null s.length()!=0){

17 o.println(s.toUpperCase());

18 //o.flush(); //一定要强制刷新让其输出来，否则不会输出

22 }

 1 package com.iotest;

 3 import java.io.BufferedInputStream;

 4 import java.io.BufferedOutputStream;

 5 import java.io.BufferedReader;

 6 import java.io.FileInputStream;

 7 import java.io.FileNotFoundException;

 8 import java.io.FileOutputStream;

 9 import java.io.IOException;

10 import java.io.InputStreamReader;

11 import java.io.PrintStream;

13 public class StandardIORedirect {

15 public static void main(String[] args) throws IOException {

16 PrintStream console = System.out;

17 BufferedInputStream in = new BufferedInputStream(new FileInputStream(“C:\Documents and Settings\01\桌面\Test\src\com\iotest\StandardIORedirect.java”));

18 PrintStream out = new PrintStream(new BufferedOutputStream(new FileOutputStream(“F:\shar\test\test9.txt”)));

19 System.setIn(in); //对标准输入流重定向

20 System.setOut(out);

21 System.setErr(out);

22 BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

23 String s;

24 while((s=br.readLine())!=null){ //从BufferedReader中读取一行数据

25 System.out.println(s);

27 out.close();

28 System.setOut(console);

31 }

六、随即访问文件类

 1 package com.iotest;

 3 import java.io.FileNotFoundException;

 4 import java.io.IOException;

 5 import java.io.RandomAccessFile;

 7 public class RandomRW {

 8 public static void main(String[] args) throws IOException {

 9 RandomAccessFile raf = new RandomAccessFile(“F:\shar\test\test10.dat”,”rw”);

10 final int DOUBLE_SIZE = 8;

11 for (int i = 0; i i++) {

12 raf.writeDouble(i);

13 System.out.print(“ “ + (double)i);

15 System.out.println();

16 raf.close();

17 RandomAccessFile raf1 = new RandomAccessFile(“F:\shar\test\test10.dat”,”rw”);

18 raf1.seek(3DOUBLE_SIZE); //找到某个位置

19 raf1.writeDouble(300); //往该位置插入数据

20 raf1.seek(5DOUBLE_SIZE);

21 raf1.writeDouble(500);

22 raf1.close();

23 RandomAccessFile raf2 = new RandomAccessFile(“F:\shar\test\test10.dat”,”r”);

24 for (int i = 0; i i++) {

25 System.out.print(“ “+raf2.readDouble());

27 raf2.close();

30 }

Java开发——28.I/O流_字符流和字节流 Java中I/O操作主要是指使用java.io包下的内容，进行输入和输出操作；输入叫做读取数据，输出叫做写出数据。主要操作文件内容，结合前面所学的File类，我们可以灵活的读取和写出文件。
Java IO(2)—缓冲字符流以及IO中的装饰者模式 详细介绍了Java IO中的缓冲字符流BufferedWriter、BufferedReader、LineNumberReader的使用方式，以及Java IO中的装饰者模式。