黑马程序员--java基础之IO流

 

IO流的规律：   

    1、首先知道IO流的体系，分为输入和输出流，输入流:InputStream,Reader.输出流：OutputStream，Writer

    2、明确源和目的，源  需要用到InputStream或者Reader；

          目的需要用到OutputSteam或者Writer；

    3、明确具体文件类型：如果是文本文件，用字符流Reader/Writer；

         如果是非文本文件，如图片，视频等，用字节流InputStream/OutputStream；

    4、通过设备确定用哪个具体对象：源分为：内存，硬盘，键盘。

         目的分为：内存，硬盘，控制台。

    5、是否需要提高效率：BufferedReader/Writer

练习一：读取一个.java文件，打印出来

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class IOStream{
    public static void main(String [] args){
        FileReader fr = null;
        try{
            fr = new FileReader("area.java");
            char [] ch = new char[1024];
            int num = 0;
            while((num = fr.read(ch))!=-1){    
                System.out.print("area.java:" + new String(ch,0,num));
            }
        }
        catch(IOException e){
            System.out.println(e.toString());
        }
        finally{
            try{
                fr.close();
            }
            catch(IOException e){
                System.out.println(e.toString());
            }          
        }      
    }
}

练习二：将一个c盘的文件复制到d盘

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class IOStream{
    public static void main(String [] args){
        FileWriter fw = null;
        FileReader fr = null;
        try{
            fw = new FileWriter("D:\\area.java");
            fr = new FileReader("area.java");
            char [] ch = new char[1024];
            int num = 0;
            while((num = fr.read(ch))!=-1){
                fw.write(ch,0,num);
            }
        }
        catch(IOException e){
            System.out.println(e.toString());
        }
        finally{
            if(fr == null)
                try{                   
                    fr.close();
                }
                catch(IOException e){
                    System.out.println(e.toString());
                }
            if(fw == null)
                try{
                    fw.close();                
                }
                catch(IOException e){
                    System.out.println(e.toString());
                }
        }      
    }
}

练习三：练习二的改进版，利用缓冲区复制文本

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class IOStream{
    public static void main(String [] args){
        BufferedReader br = null;
        BufferedWriter bw = null;
        try{           
            br = new BufferedReader(new FileReader("area.java"));
            bw = new BufferedWriter(new FileWriter("D:\\area.java"));
            String s = null;
            while((s = br.readLine())!=null){
                bw.write(s);
                bw.newLine();
                bw.flush();
            }
        }
        catch(IOException e){
            System.out.println(e.toString());
        }
        finally{
            if(bw==null)
                try{
                    bw.close();                
                }
                catch(IOException e){
                    System.out.println(e.toString());
                }
            if(br==null)
                try{                   
                    br.close();
                }
                catch(IOException e){
                    System.out.println(e.toString());
                }  
        }
    }
}

练习四：拷贝一张图片；

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class IOStream{
    public static void main(String [] args){
        FileInputStream fis = null;
        FileOutputStream fos = null;
        try{
            fis = new FileInputStream("34.jpg");
            fos = new FileOutputStream("D:\\background.jpg");
            byte [] bt = new byte[1024];
            int num = 0;
            while((num = fis.read(bt))!=-1){
                fos.write(bt);
            }
        }
        catch(IOException e){
            System.out.println(e.toString());
        }
        finally{
            if(fis==null)
                try{
                    fis.close();
                }
                catch(IOException e){
                    System.out.println(e.toString());
                }
            if(fos==null)
                try{
                    fos.close();
                }
                catch(IOException e){
                    System.out.println(e.toString());
                }  
        }
    }
}
posted @ 2013-04-06 00:05  郭彦君  阅读(120)  评论(0)    收藏  举报