字符缓冲流：  开发时候建议使用缓冲流，速度和效率更快。
BufferedReader的api部分：

BufferedInputStream 部分api： 可以看出

BufferedInputStream是没有readLine()方法。更多具体，请自行查看api文档

package cn.bean.demo.io.buffer;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;

public class BufferedReaderTest {

	public static void main(String[] args) {
		
		testReadWrite();
	}
	
	static void testReadWrite(){


		try (
				Reader read = new FileReader("String1.txt");
				BufferedReader buff = new BufferedReader(read);
				Writer writer = new FileWriter("String2.txt");
				BufferedWriter buffWrite = new BufferedWriter(writer);
				) 
		{
		//每次读取的数据放入到缓冲区
		  char[] ch=new char[10];
		  // 每次读取的时候放入到缓冲区的实际字符个数
		  int len=0;
		  while((len=buff.read(ch))!=-1){
			  buffWrite.write(ch, 0, len);;
		  }

		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	
	
	}

	static void testReadWriteLine(){

		try (
				Reader read = new FileReader("String1.txt");
				BufferedReader buff = new BufferedReader(read);
				Writer writer = new FileWriter("String2.txt");
				BufferedWriter buffWrite = new BufferedWriter(writer);
				) 
		{
			
			String content=null;
			int i=0;
			while((content=buff.readLine())!=null){
				if(i!=0){
					//第一次不换行，当第二次写的时候换行
					buffWrite.write("\n");
				}
				buffWrite.write(content);
				i++;
				
			}

		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	
	}
}

package cn.bean.demo.io.buffer;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class BufferedInputStreamTest {

    public static void main(String[] args) {
        testReadWriteReadLine();
    }

    static void testReadWriteReadLine() {

        try (InputStream in = new FileInputStream("String1.txt");
                BufferedInputStream buffer = new BufferedInputStream(in);
                OutputStream out = new FileOutputStream("String2.txt");
                BufferedOutputStream bufferWrite = new BufferedOutputStream(out);) {
                //BufferedInputStream没有readLine方法
                 //创建一个用来存放每次读取的数据的缓冲区
                 byte[] b=new byte[20];
                  //每次读取，并放入到缓冲区的实际字符个数
                 int len=0;
                 while((len=buffer.read(b))!=-1){
                     bufferWrite.write(b, 0, len);
                 }
            

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}