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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
	}
}

总结

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