java中所谓流通俗来讲就是数据源的传输，我们的文件，视屏，对象都可以叫做数据源，io将他们那转换为可以在不同程序中传输的数据，众所周知电脑存储是二进制，而处理时常遇到字节和字符的写入和写出，分别以8位或者16位二进制表示，
我们先来看文件，文件就是电脑中存储的音频，视屏，图片，文本文件等等，java中用File表示文件，下面程序表示过滤出隐藏文件
File[] files = new File(".").listFiles(new FilenameFilter() {@Overridepublic boolean accept(File dir, String name) {return dir.isHidden();}});//简写后形式如下File[] files1 = new File(".").listFiles(File::isHidden);//File的重要方法File file = new File("src/main/resources/ss.txt");file.mkdir();//父路径必须存在否则报错file.mkdirs();//父路径不存在则创建file.exists();//判断是文件否存在
字节的输入输出实例，记住要关闭流，这里用了java7以后语法不用显示的关闭流的方式
//放入try语句中之后会自动关闭流try( FileInputStream fileInputStream =new FileInputStream(new File("src/main/resources/data.csv"));FileOutputStream fileOutputStream = new FileOutputStream(new File("src/main/resources/data1.csv"))) {int len=0;byte[] chars =new byte[1024];//一次读1024字节，写1024字节while((len=fileInputStream.read(chars))!=-1){System.out.println(new String(chars,0,len));fileOutputStream.write(chars,0,len);}}catch (Exception E){E.printStackTrace();}//带缓冲的字节输入输出流，能提高效率，用的是包装设计模式，FileOutputStream的第二个参数为true时将会在之前文件中添加而不是覆盖try(BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream("."));BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(".",true))){int len=0;byte[] chars =new byte[1024];while((len=bufferedInputStream.read(chars))!=-1){bufferedOutputStream.write(chars,0,len);}}catch (Exception e){e.printStackTrace();}
字符的输入输出实例
//BufferedReader字符输入缓冲，BufferedWriter字符输出缓冲try(BufferedReader bufferedReader = new BufferedReader(new FileReader("."));BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("."))){int len=0;char[] chars =new char[1024];while((len=bufferedReader.read(chars))!=-1){// bufferedReader.readLine();BufferedReader特有方法，读一行数据bufferedWriter.write(chars,0,len);bufferedWriter.newLine();//BufferedWriter特有方法换行}}catch (Exception e){e.printStackTrace();}
转换实例
//这里我们也用缓冲字符输出和输入类进行包装，提高转换效率try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream("src/main/resources/data.csv")));BufferedWriter bufferedWriter1 = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("src/main/resources/data1.csv", true)));) {int len = 0;while (len != -1) {char[] arr = new char[1024];if ((len = bufferedReader.read(arr)) != -1) {bufferedWriter1.newLine();bufferedWriter1.write(arr, 0, len);}}} catch (Exception e) {e.printStackTrace();}
当然也可以设置输入输出的编码
new InputStreamReader(new FileInputStream(new File("e:/123.doc")),"utf-8"); new OutputStreamWriter(new FileOutputStream(new File("e:/456.doc")),"utf-8");
