java IO 2020/10/25

流

1、流是一组有序的数据序列；
2、以先进先出方式发送信息的通道

按流向分

输出流
	OutputStream
	InputStream
输入流
	Reader
	Writer

按处理数据单元分

字节流
	字节输入流InputStream基类
		int read();
		int read(byte[ ] b);
		int read(byte[ ] b,int off,int len);
		void close();
		int available();

    FileInputStream reader =null;
        try{
            reader = new FileInputStream("myfile/cc.txt");
            byte[] b = new byte[1024]; //字节读取到数组中
            int len ;  //读取到的字节数
            while ((len=reader.read(b))!=-1){
                for (int i = 0; i <len ; i++) {
                    System.out.print((char) b[i]);
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

	字节输出流OutputStream基类
		void write(int b);
		void write(byte[ ] b);
		void write(byte[ ] b,int off,int len);
		void close();
		void flush();强制把缓冲区的数据写出输出流中

        FileOutputStream writer =null;
        try{
            writer = new FileOutputStream("myfile/cc.txt",true) ; //向原文件追加
            String info = "大数据";
            byte[] infos =info.getBytes();   //将字符串转换为字节数组
            writer.write(infos);
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                writer.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

字符流
	字符输入流Reader基类
		子类：BufferReader 
		int read();
		int read(char[ ] c);
		int read(char[ ] c,int off,int len);
		void close();

        FileReader reader1 =null;
        BufferedReader reader2 = null;
        try{
            reader1 = new FileReader("myfile/cc.txt") ;
            reader2 = new BufferedReader(reader1);
            String s =null;
            while ((s=reader2.readLine())!=null){
                System.out.println(s);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                reader2.close();
                reader1.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

	字符输出流Writer基类
		子类：BufferWriter 
		void write(String str);
		void write(String str,int off,int len);
		void close();
		void flush();强制把缓冲区的数据写出输出流中

    File file = new File("myfile/aa.txt");
        FileWriter writer2 =null;
        BufferedWriter writer3 =null;
        try{
            writer2 = new FileWriter(file,true) ;
            writer3 = new BufferedWriter(writer2);
            writer3.write("大数据");
            writer3.newLine();   //换行
            writer3.write("大数据");
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                writer3.close();
                writer2.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }