读取文件内容

public class UseBuffer {
    public static  void main(String[] args) throws IOException{
                          final int  SIZE = 1024;
                          File fileIn = new File ("./src/txt/","1.txt");
                          FileInputStream in = 
                                        new FileInputStream(fileIn);
                          File fileOut = new File("./src/txt/","2.txt");
                          FileOutputStream out = 
                                         new FileOutputStream(fileOut);
                        //创建byte数组
                          byte[] buff = new byte[SIZE];
                        
                          int num = in.read(buff);
                          while(num!=-1){
                                 out.write(buff,0,num); 
                                 num = in.read();
                          }
                          in.close();
                          out.close();
    }
}    

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileTest2 {
    public static void main(String[] args) throws IOException {
        //将变量存入 System
        System.setProperty("use.dir", "./src/picture");
        //得到Properties
        String usedir = System.getProperty("use.dir");
        System.out.println("用户路径为  ："+usedir);
        
        File file = new File(usedir,"IMAG0056.jpg");
        System.out.println("check whether the file is exsist : "+file.isFile());
        System.out.println("check the length of the file :"+file.length());
        
        File fileOut = new File(usedir,"IMAG0057.jpg");
        //输入流
        FileInputStream in = new FileInputStream(file);
        //输出流 
        FileOutputStream out =  new FileOutputStream(fileOut);
        
        //建立缓冲区
        int SIZE  = 1024;
        byte[] buff = new byte[SIZE];
        
        //从输入流中读取内容
        int num = in.read(buff);
        //写入到输出流之中
        while(num!=-1){
            out.write(buff);
            num = in.read(buff);
        }
        in.close();
        out.close();
    }
}