4.典型实现：

@Test

    public void test1() throws IOException {

        FileInputStream fis = new FileInputStream("dbcp.txt");

//        InputStreamReader isr = new InputStreamReader(fis);//使用系统默认的字符集

        //参数2指明了字符集，具体使用哪个字符集，取决于文件dbcp.txt保存时使用的字符集

        InputStreamReader isr = new InputStreamReader(fis,"UTF-8");//使用系统默认的字符集

        char[] cbuf = new char[20];

        int len;

        while((len = isr.read(cbuf)) != -1){

            String str = new String(cbuf,0,len);

            System.out.print(str);

        }

        isr.close();

    }

/*

此时处理异常的话，仍然应该使用try-catch-finally

综合使用InputStreamReader和OutputStreamWriter

 */

@Test

public void test2() throws Exception {

    //1.造文件、造流

    File file1 = new File("dbcp.txt");

    File file2 = new File("dbcp_gbk.txt");

    FileInputStream fis = new FileInputStream(file1);

    FileOutputStream fos = new FileOutputStream(file2);

    InputStreamReader isr = new InputStreamReader(fis,"utf-8");

    OutputStreamWriter osw = new OutputStreamWriter(fos,"gbk");

    //2.读写过程

    char[] cbuf = new char[20];

    int len;

    while((len = isr.read(cbuf)) != -1){

        osw.write(cbuf,0,len);

    }

    //3.关闭资源

    isr.close();

    osw.close();

}