java ByteArrayInputStream用法

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;

public class tmp
{
        public static void main(String args[]) throws Exception
        {
                DataInputStream r = new DataInputStream(System.in);

                byte[] data = new byte[1024];
                int len;

                len = r.read(data, 0, data.length);
                System.out.println(len);

                ByteArrayInputStream in = new ByteArrayInputStream(data, 0, len);
                int c;

                while (true)
                {
                        c = in.read();
                        if (c == -1)
                                break;
                        System.out.println((char) c);
                }

                r.close();
                in.close();
        }
}