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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