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
import java.io.*;
public class FileReaderDemo {
public static void main(String[] args) {
FileReader fr = null;
try{
fr = new FileReader("FileWriterDemo.txt");
int ch =0;
while((ch = fr.read())!=-1){
System.out.print((char)ch);
}
}
catch(IOException e){
System.out.println(e.toString());
}
finally{
try{
if(fr!=null)
fr.close();
}
catch(IOException e){
System.out.println(e.toString());
}
}
}
}
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
import java.io.FileReader;
import java.io.IOException; public class FileReaderDemo2 { public static void main(String[] args) {
FileReader fr = null;
try{
fr = new FileReader("FileWriterDemo.txt");
//定义字符数组用于存储读到的字符
char[] buf = new char[1024];
int aLength = fr.read(buf);
for(int x = 0;x< aLength;x++)
{
System.out.print(buf[x]);
} }
catch(IOException e){
System.out.println(e.toString());
}
finally{
try{
if(fr!=null)
fr.close();
}
catch(IOException e){
System.out.println(e.getStackTrace());
}
} } }
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。
import java.io.*;
public class BufferedReaderDemo {
public static void main(String[] args) {
//创建一个读取流对象
FileReader fr = null;
try{
fr = new FileReader("xinwen.txt");
//加入缓冲技术，提高读取效率
BufferedReader bufr = new BufferedReader(fr);
String line = null;
while((line=bufr.readLine())!=null){
System.out.println(line);
}
bufr.close();
}
catch(IOException e){
e.printStackTrace();
}
finally{
try{
if(fr!=null)
fr.close();
}
catch(IOException e){
e.printStackTrace();
}
}
}
}
FileWriter是OutputStreamWriter的子类，而OutputStreamWriter是Writer的子类。Writer系列是输出字符流。
import java.io.*;
public class FileWriterDemo {
public static void main(String[] args)throws IOException {
FileWriter fw = null;
try {
fw = new FileWriter("FileWriterDemo.txt",true);
fw.write("2015");
fw.write("\r\n");
fw.write("一起努力！");
fw.flush();
}
catch(IOException e){
System.out.println(e.toString());
}
finally{
try{
if(fw!=null)
fw.close();
}
catch(IOException e){
System.out.println(e.toString());
}
}
}
}
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
import java.io.*;
public class FileCopyDemo {
public static void main(String[] args) {
//copy1();
copy2();
}
//读一个字符就存一个
public static void copy1(){
//创建目的文件
FileWriter fw = null;
//与已有文件关联
FileReader fr = null;
try{
fw = new FileWriter("/home/owen/news_copy.txt");
fr = new FileReader("news.txt");
int ch = 0;
while((ch=fr.read())!=-1){
fw.write(ch);
}
}
catch(IOException e){
System.out.println(e.getStackTrace());
}
finally{
try{
if(fw!=null)
fw.close();
if(fr!=null)
fr.close();
}
catch(IOException e){
System.out.println(e.getStackTrace());
}
}
}
public static void copy2(){
FileWriter fw = null;
FileReader fr = null;
try{
fw = new FileWriter("news_copy2.txt");
fr = new FileReader("news.txt");
char[] buf = new char[1024];
int len = 0;
while((len = fr.read(buf))!=-1){
fw.write(buf,0,len);
}
}
catch(IOException e){
throw new RuntimeException("读写失败");
}
finally{
if(fr!=null){
try{
fr.close();
}
catch(IOException e){
System.out.println(e.getStackTrace());
}
}
if(fw!=null){
try{
fw.close();
}
catch(IOException e){
System.out.println(e.getStackTrace());
}
}
}
}
}
方法二，使用缓冲技术
import java.io.*;
public class CopyByBuffered {
public static void main(String[] args) {
BufferedReader bufr = null;
BufferedWriter bufw = null;
try{
bufr = new BufferedReader(new FileReader("BufferedReaderDemo.java"));
bufw = new BufferedWriter(new FileWriter("BufferedReaderDemo_copy.txt"));
String line = null;
while((line = bufr.readLine())!=null){
bufw.write(line);
bufw.flush();
bufw.newLine();
}
}
catch(IOException e){
throw new RuntimeException("复制失败！");
}
finally{
try{
if(bufr!=null)
bufr.close();
}
catch(IOException e){
throw new RuntimeException("Read file mission failed!");
}
try{
if(bufw!=null)
bufw.close();
}
catch(IOException e){
throw new RuntimeException("Write file mission failed!");
}
}
}
}