FileInputStream实现读取文件内容并输出到屏幕上

java输入输出流是站在程序的角度来说的。从文件中读取数据用输入流，向文件中写数据用输出流。

package com.janson.day20180827;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class TestFileInputStream {
    public static void main(String[] args) {
        FileInputStream in = null;
        int f = 0;
        try {
            in = new FileInputStream(System.getProperty("user.dir") + "\src\com\janson\day20180827\TestFileInputStream.java");
        }catch (FileNotFoundException e) {
            e.printStackTrace();
            System.out.println("找不到指定文件");
            System.exit(-1);
        }

        try {
            long num =0L;
            while ((f=in.read()) != -1) {
                System.out.print((char)f);
                num ++;
            }
            System.out.println("一共读取了"+ num + "个字节");
        }catch (IOException e) {
            System.out.println("文件读取错误");
            System.exit(-1);
        }
    }
}