java的inputstream, outputstream, reader和writer的比较

java的文件读写有多种方式，在此通过代码做以下比较。

比较一：FileWriter和FileReader

public class MyCode1 {

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

           File f = new File("my.txt");

           FileWriter fw = new FileWriter(f);
           fw.write("HELLO");
           fw.close();

           FileReader fr = new FileReader(f);
           System.out.println((char)fr.read());
           fr.close();

       }
}

输出: H

可见，FileWriter可以批量写入，但是FileReader每次只能读取一个字符。

比较二：OutputStream和InputStream

public class MyCode1 {

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

           File f = new File("my.txt");

           char[] data = new char[]{‘H‘, ‘E‘, ‘L‘, ‘L‘, ‘O‘};

           OutputStream os = new FileOutputStream(f);
           os.write(data[0]);
           os.close();

           InputStream is = new FileInputStream(f);
           System.out.println((char)is.read());
           is.close();

       }
}

输出: H

可见，OutputStream和InputStream每次只可以读写一个字符。

比较三：OutputStreamWriter和InputStreamReader

public class MyCode1 {

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

           File f = new File("my.txt");

           OutputStream os = new FileOutputStream(f);
           OutputStreamWriter osw = new OutputStreamWriter(os);
           osw.write("HELLO");
           osw.close();
           os.close();

           InputStream is = new FileInputStream(f);
           InputStreamReader isr = new InputStreamReader(is);
           System.out.println((char)isr.read());
           isr.close();
           is.close();

       }
}

输出: H

可见，OutputStreamWriter可以批量写入，但是InputStreamReader每次只能读取一个字符。效果同FileWriter和FileReader。

比较四：BufferedWriter和BufferedReader

public class MyCode1 {

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

           File f = new File("my.txt");

           OutputStream os = new FileOutputStream(f);
           OutputStreamWriter osw = new OutputStreamWriter(os);
           BufferedWriter bw = new BufferedWriter(osw);
           bw.write("HELLO");
           bw.close();
           osw.close();
           os.close();

           InputStream is = new FileInputStream(f);
           InputStreamReader isr = new InputStreamReader(is);
           BufferedReader br = new BufferedReader(isr);
           System.out.println(br.readLine());
           isr.close();
           is.close();

       }
}

输出: HELLO

可见，BufferedWriter和BufferedReader可以批量读写。