将C盘一个文本文件复制到D盘。

public class CopyText {

    public static void main(String[] args) throws IOException
    {
        copy_2();

    }
    public static void copy_2()
    {
        FileWriter fw = null;
        FileReader fr = null;
        try
        {
            fw = new FileWriter("SystemDemo_copy.txt");
            fr = new FileReader("SystemDemo.java");
            
            char[] buf = new char[1024];
            
            int len = 0;
            while((len=fr.read(buf))!=-1)
            {
                fw.write(buf,0,len);
            }
        }
        catch(IOException e)
        {
            throw new RuntimeException("读写失败");
        }
        finally
        {
            if(fr!=null)
                try
                {
                    fr.close();
                }
                catch(IOException e)
                {
                }
            if(fw!=null)
                try
                {
                    fw.close();
                }
                catch(IOException e)
                {
                }
        }
    }
    
    //从C盘读一个字符，就往D盘写一个字符。
    public static void copy_1() throws IOException
    {
        //创建目的地。
        FileWriter fw = new FileWriter("RuntimeDemo_copy.txt");
        
        //与已有文件关联。
        FileReader fr = new FileReader("RuntimeDemo.java");
        
        int ch = 0;
        
        while((ch=fr.read())!=-1)
        {
            fw.write(ch);
        }
        fw.close();
        fr.close();
    }
    

}