4、IO--字节转换流

整个Java的I/O包中实际上分为字节流和字符流

还存在一组”字节流--字符流“的转换类

1、OutputStreamWriter：是Writer的子类，将输出的字符流变为字节流

　　即将一个字符流的输出对象变为字节流的输出对象

2、InputStreamReader：是Reader的子类，将输入的字节流转换为字符流

　　即将一个字节流的输入对象变为字符流的输入对象

关闭规则：

由里到外

字符流转换为字节流OutputStreamWriter

    public static void main(String[] args) throws IOException {
        
        //1、
        File file = new File("d:\test.txt");
        OutputStream out = new FileOutputStream(file);
        
        //2、
        Writer writer = null;
        writer = new OutputStreamWriter(out);
        
        //3、
        writer.write("天长地久");
        
        //4、
        writer.close();
        out.close();
        
    }

 字节流转换为字符流InputStreamReader

    public static void main(String[] args) throws IOException {
        
        //1、
        File file = new File("d:\test.txt");
        InputStream in = new FileInputStream(file);
        
        //2、
        InputStreamReader reader = null;
        reader = new InputStreamReader(in);
        
        //3、
        int res = 0;
        int len = 0;
        char [] b = new char[(int) file.length()];
        
        while((res = reader.read()) !=-1){
            b[len] = (char) res;
            len++;
        }
        
        //4、
        reader.close();
        in.close();
    
        System.out.println(new String(b));
    }
}