InputStream只能读一遍

InputStream在被读出后，在下次读取的时候会出现null。因此在下次读取或者利用InputStream的时候要把它写回去。

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;


public class Reader {
	public static void main(String[] args) throws IOException{
		InputStream in = new FileInputStream(new File("text.txt"));
		BufferedReader reader = new BufferedReader(new InputStreamReader(in));
		String str = null;
		
		StringBuffer sb = new StringBuffer();
		while((str = reader.readLine())!=null){
			System.err.println(str);
			sb.append(str);
		}
		ByteArrayInputStream bis = new ByteArrayInputStream(sb.toString().getBytes());
		BufferedReader reader2 = new BufferedReader(new InputStreamReader(bis));
		String str2 = null;
		while((str2 = reader2.readLine())!=null){
			System.out.println(str2);
		}
	}
}