BufferedReader 中的缓冲区大小是多少？

构造函数中的缓冲区大小是什么意思？

BufferedReader(Reader in, int size)

正如我所写的程序：

import java.io.*;
class bufferedReaderEx{
    public static void main(String args[]){
        InputStreamReader isr = null;
        BufferedReader br = null;
            try{
                isr = new InputStreamReader(System.in);
//              System.out.println("Write data: ");
//              int i = isr.read();
//              System.out.println("Data read is: " + i);
                //Thus the InputStreamReader is useful for reading the character from the stream
                System.out.println("Enter the data to be read by the bufferedReader: ");
                //here isr is containing the lnefeed already so this is needed to be flushed.
                br = new BufferedReader(isr, 2);
                String str = br.readLine();
                System.out.println("The data is : :" +  str);
            }catch(IOException e){
                System.out.println("Can't read: " + e.getMessage());
            }
    }
}

输出：

Enter the data to be read by the bufferedReader: Hello world and hello world again
The data is: Hello world and hello world again

然后缓冲区大小意味着什么，因为我打算它只读取两个字符。但事实并非如此。