java学习笔记之文件输出输入流

节点流类型：

举个栗子：

package io;

import java.io.*;

public class TestFileInputStream {
    public static void main(String[] args) {
        int b = 0;
        FileInputStream in = null;
        try {
            in = new FileInputStream("d:/1.txt");
        } catch (FileNotFoundException e) {
            System.out.println("找不到指定文件");
            System.exit(-1);
        }

        try {
            long num = 0;
            while ((b = in.read()) != -1) {
                System.out.print((char) b);
                num++;
            }
            in.close();
            System.out.println();
            System.out.println("共读取了 " + num + " 个字节");
        } catch (IOException e1) {
            System.out.println("文件读取错误");
            System.exit(-1);
        }
    }
}

 搞不明白的是为什么非要用一个int型的b去接收，不接收又不行，为啥

package io;

import java.io.*;
public class TestFileOutputStream {
  public static void main(String[] args) {
      int b = 0;
      FileInputStream in = null;
      FileOutputStream out = null;
      try {
        in = new FileInputStream("d:/share/java/HelloWorld.java");
        out = new FileOutputStream("d:/share/java/io/HW.java");
        while((b=in.read())!=-1){
          out.write(b);
        }
        in.close(); 
        out.close();
      } catch (FileNotFoundException e2) {
        System.out.println("找不到指定文件"); System.exit(-1);
      } catch (IOException e1) {
        System.out.println("文件复制错误"); System.exit(-1);
      }
      System.out.println("文件已复制");
  }
}