以字符为单位的IO

import java.io.*;
public class WriterTest {
    public static void main(String[] args) throws Exception {
        FileOutputStream fos = new FileOutputStream("D://java//1.txt");
        OutputStreamWriter osw = new OutputStreamWriter(fos);
        BufferedWriter bw = new BufferedWriter(osw);
        bw.write("123456789");
        bw.close();

        FileInputStream fis = new FileInputStream("D://java//1.txt");
        InputStreamReader isr = new InputStreamReader(fis);
        BufferedReader br = new BufferedReader(isr);
        System.out.print(br.readLine());
        br.close();


        InputStreamReader isrin = new InputStreamReader(System.in);
        BufferedReader brin = new BufferedReader(isrin);
        String s;
        while((s = brin.readLine()) != null) {
            System.out.println(s);
        }
        brin.close();

    }
}