FileReader是InputStreamReader的子类，InputStreamReader是Reader的子类。Reader系列是输入字符流。
1.一个字符一个字符的读取
1 import java.io.*;
2
3 public class FileReaderDemo {
4
5 public static void main(String[] args) {
6 FileReader fr = null;
7 try{
8 fr = new FileReader("FileWriterDemo.txt");
9 int ch =0;
10 while((ch = fr.read())!=-1){
11 System.out.print((char)ch);
12 }
13 }
14 catch(IOException e){
15 System.out.println(e.toString());
16 }
17 finally{
18 try{
19 if(fr!=null)
20 fr.close();
21 }
22 catch(IOException e){
23 System.out.println(e.toString());
24 }
25
26 }
27
28 }
29
30 }
2.使用字符数组临时存储读取的字符，数组长度可以自定义
1 import java.io.FileReader;
2 import java.io.IOException;
3
4 public class FileReaderDemo2 {
5
6 public static void main(String[] args) {
7 FileReader fr = null;
8 try{
9 fr = new FileReader("FileWriterDemo.txt");
10 //定义字符数组用于存储读到的字符
11 char[] buf = new char[1024];
12 int aLength = fr.read(buf);
13 for(int x = 0;x< aLength;x++)
14 {
15 System.out.print(buf[x]);
16 }
17
18 }
19 catch(IOException e){
20 System.out.println(e.toString());
21 }
22 finally{
23 try{
24 if(fr!=null)
25 fr.close();
26 }
27 catch(IOException e){
28 System.out.println(e.getStackTrace());
29 }
30 }
31
32 }
33
34 }
为了提高读取效率，加入BufferedReader(Reader in)缓冲技术，该类可以使用readLine方法，一次读取一行。
1 import java.io.*;
2
3 public class BufferedReaderDemo {
4
5 public static void main(String[] args) {
6 //创建一个读取流对象
7 FileReader fr = null;
8 try{
9 fr = new FileReader("xinwen.txt");
10 //加入缓冲技术，提高读取效率
11 BufferedReader bufr = new BufferedReader(fr);
12
13 String line = null;
14 while((line=bufr.readLine())!=null){
15 System.out.println(line);
16 }
17 bufr.close();
18 }
19 catch(IOException e){
20 e.printStackTrace();
21 }
22 finally{
23 try{
24 if(fr!=null)
25 fr.close();
26 }
27 catch(IOException e){
28 e.printStackTrace();
29 }
30 }
31 }
32 }
FileWriter是OutputStreamWriter的子类，而OutputStreamWriter是Writer的子类。Writer系列是输出字符流。
1 import java.io.*;
2
3 public class FileWriterDemo {
4
5 public static void main(String[] args)throws IOException {
6 FileWriter fw = null;
7 try {
8 fw = new FileWriter("FileWriterDemo.txt",true);
9 fw.write("2015");
10 fw.write("\r\n");
11 fw.write("一起努力！");
12
13 fw.flush();
14 }
15 catch(IOException e){
16 System.out.println(e.toString());
17 }
18 finally{
19 try{
20 if(fw!=null)
21 fw.close();
22 }
23 catch(IOException e){
24 System.out.println(e.toString());
25 }
26 }
27 }
28
29 }
为了提阿写入效率，使用BufferedWriter(Writer wr)缓冲技术，该类中的newLine方法可以输出一个换行符，而且是跨平台的。
把输入、输出结合起来，模拟复制文件。方法一，不使用缓冲技术
1 import java.io.*;
2
3 public class FileCopyDemo {
4
5 public static void main(String[] args) {
6
7 //copy1();
8 copy2();
9 }
10 //读一个字符就存一个
11 public static void copy1(){
12 //创建目的文件
13 FileWriter fw = null;
14 //与已有文件关联
15 FileReader fr = null;
16
17 try{
18 fw = new FileWriter("/home/owen/news_copy.txt");
19 fr = new FileReader("news.txt");
20 int ch = 0;
21 while((ch=fr.read())!=-1){
22 fw.write(ch);
23 }
24 }
25 catch(IOException e){
26 System.out.println(e.getStackTrace());
27 }
28 finally{
29 try{
30 if(fw!=null)
31 fw.close();
32 if(fr!=null)
33 fr.close();
34 }
35 catch(IOException e){
36 System.out.println(e.getStackTrace());
37 }
38 }
39 }
40 public static void copy2(){
41 FileWriter fw = null;
42 FileReader fr = null;
43 try{
44 fw = new FileWriter("news_copy2.txt");
45 fr = new FileReader("news.txt");
46
47 char[] buf = new char[1024];
48 int len = 0;
49 while((len = fr.read(buf))!=-1){
50 fw.write(buf,0,len);
51 }
52 }
53 catch(IOException e){
54 throw new RuntimeException("读写失败");
55 }
56 finally{
57 if(fr!=null){
58 try{
59 fr.close();
60 }
61 catch(IOException e){
62 System.out.println(e.getStackTrace());
63 }
64 }
65 if(fw!=null){
66 try{
67 fw.close();
68 }
69 catch(IOException e){
70 System.out.println(e.getStackTrace());
71 }
72 }
73 }
74 }
75
76 }
方法二，使用缓冲技术
1 import java.io.*;
2
3 public class CopyByBuffered {
4
5 public static void main(String[] args) {
6 BufferedReader bufr = null;
7 BufferedWriter bufw = null;
8 try{
9 bufr = new BufferedReader(new FileReader("BufferedReaderDemo.java"));
10 bufw = new BufferedWriter(new FileWriter("BufferedReaderDemo_copy.txt"));
11
12 String line = null;
13 while((line = bufr.readLine())!=null){
14 bufw.write(line);
15 bufw.flush();
16 bufw.newLine();
17 }
18 }
19 catch(IOException e){
20 throw new RuntimeException("复制失败！");
21 }
22 finally{
23 try{
24 if(bufr!=null)
25 bufr.close();
26 }
27 catch(IOException e){
28 throw new RuntimeException("Read file mission failed!");
29 }
30 try{
31 if(bufw!=null)
32 bufw.close();
33 }
34 catch(IOException e){
35 throw new RuntimeException("Write file mission failed!");
36 }
37 }
38
39 }
40
41 }
时间： 2025-01-02 00:21:24