Java IO流相关知识代码解析

一、IO流的分类

字符流

Reader
InputStreamReader（节点流）
BufferedReader（处理流）
Writer
OutputStreamWriter（节点流）
BufferedWriter（处理流）
PrintWriter

字节流

InputStream
FileInputStream（节点流）
BufferedInputStream（处理流）
ObjectInputStream（处理流）
PrintStream
OutputStream
FileOutputStream（节点流）
BufferedOutputStream（处理流）
ObjectOutputStream（处理流）

断点处理的流

RandomAccessfile

二、IO流的用法

1、转换流的用法

    FileInputStream in = new FileInputStream(newFile(""));    
     Readerreader = new InputStreamReader(in);//字节转字符
     FileOutputStreamout = new FileOutputStream(newFile(""));
     Writer writer = new OutputStreamWriter(out);//字符转字节

2、对象序列化,对象需要实现Serializable接口

     FileOutputStreamfileOutputStream = new FileOutputStream("C:\\Users\\lx\\Desktop\\Record.txt");
     ObjectOutputStreamobjectOutputStream = new ObjectOutputStream(fileOutputStream);
     objectOutputStream.writeObject(object);//向指定文件写入对象object
     objectOutputStream.close();

FileInputStreamfileInputStream = new FileInputStream("C:\\Users\\lx\\Desktop\\Record.txt");
     ObjectInputStreamobjectInputStream = new ObjectInputStream(fileInputStream);
     object = objectInputStream.readObject();//读取得到对象object
     fileInputStream . lose();

3、断点的运用

public class Copy extends Thread{
//可以利用多线程实现拷贝  
longstart;
longend;
Filesorce;
Filetargetdir;
publicCopy() {
}
publicCopy(longstart,long end, File sorce, File targetdir) {
//利用构造方法传递需要拷贝的长度，拷贝开始位置，以及目标文件和源文件
super();
this.start= start;
this.end= end;
this.sorce= sorce;
this.targetdir= targetdir;
}
@Override
  publicvoid run(){
try{
RandomAccessFilesouceRaf = new RandomAccessFile(sorce,"r");
RandomAccessFiletargetRaf = new RandomAccessFile(newFile(targetdir,sorce.getName()),"rw");
souceRaf.seek(start);
targetRaf.seek(start);
intlen= 0;
byte[]bs = new byte[1024];
longseek;
System.out.println(start+"---->"+end+this.getName());
while((len= souceRaf.read(bs))!=-1){
targetRaf.write(bs, 0, len);
seek= souceRaf.getFilePointer();
//获取断点位置
if(seek== end){
break;
}
}
targetRaf.close();
souceRaf.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
}

4、字节流的用法

public class Test_InputStream {
//利用字节流获取文本文件内容，但是容易出现问题
/*  
 //可能出现int长度越界
 public static void main(String[] args) throws IOException {
   InputStream inputStream = new FileInputStream(new File("C:\\Users\\lx\\Desktop\\test\\33.txt"));
   byte[] b = new byte[inputStream.available()];  
   inputStream.read(b);
   String str = new String(b);
   System.out.println(str);
 }
*/
//可能出现乱码    
public static void main(String[] args) throws IOException {
File file = new File("C:\\Users\\lx\\Desktop\\test\\33.txt");
InputStream inputStream = new FileInputStream(file);
//统计每次读取的实际长度
int len = 0;
//声明每次读取1024个字节
byte[] b = new byte[2];
StringBuffer sBuffer = new StringBuffer();
while((len=inputStream.read(b))!=-1){
sBuffer.append(new String(b,0,len));
}
System.out.println(sBuffer.toString());
}
}
//利用字节流拷贝文件
public void copy(File sourceFile, File targetDir) {
//
FileInputStreamfileInputStream = null;
FileOutputStreamfileOutputStream = null;
fileInputStream= new FileInputStream(sourceFile);
FiletargetFile = new File(targetDir,sourceFile.getName());
fileOutputStream= new FileOutputStream(targetFile);
byte[]b = new byte[1024];
intlen = 0;
while((len= fileInputStream.read(b)) != -1) {
fileOutputStream.write(b, 0, len);
}
}

5、缓存字符流的用法

publicstatic void main(String[] args) throws IOException {
//缓存字符流实现写入文件
InputStreamin = System.in;
Readerreader = new InputStreamReader(in);
BufferedReaderbr = new BufferedReader(reader);
BufferedWriterbw = new BufferedWriter(new FileWriter(new File("src/1.txt")));
Strings="";
while((s=br.readLine())!=null) {
bw.write(s);
bw.newLine();
bw.flush();
//字符流千万不要忘了flush!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
}
}

来源：http://blog.csdn.net/qq_24065713/article/details/76407833