BufferedInputStream与BufferedOutputStream用法简介

BufferedInputStream是带缓冲区的输入流，默认缓冲区大小是8M，能够减少访问磁盘的次数，提高文件读取性能；BufferedOutputStream是带缓冲区的输出流，能够提高文件的写入效率。BufferedInputStream与BufferedOutputStream分别是FilterInputStream类和FilterOutputStream类的子类，实现了装饰设计模式。
BufferedInputStream类的例子如下：

import java.io.File;
import java.io.InputStream;
import java.io.FileInputStream;
import java.io.BufferedInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class BufferedInputStreamDemo01{

    // 声明常量
        public static final int SIZE=1024;

    public static void main(String[] args){
       //变量声明
           File f=null;
       InputStream input=null;
       BufferedInputStream bis=null;
           StringBuilder strBuild=null;
       SimpleDateFormat sdf=null;
       Date d=null;
           long start=0L;
       long end=0L; 

          try{
          sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
          
          strBuild=new StringBuilder();
                  start=System.currentTimeMillis();
          d=new Date();
          if(d!=null){
                  d.setTime(start);
         }
          System.out.println("程序开始执行时间:"+sdf.format(d));

      f=new File("d:"+File.separator+"demo.txt");
          input=new FileInputStream(f);
          // 指定文件带缓冲区的读取流且指定缓冲区大小为2KB
      bis=new BufferedInputStream(input,2*SIZE);
          int bisLength=bis.available();
          int readLength=0;
          byte[] byteArray=new byte[SIZE];
          int tmp=0;
          while((tmp=bis.read(byteArray))!=-1){ 
                strBuild.append(new String(byteArray,0,tmp));
        System.out.println("每次读取字节数量:"+tmp);
        System.out.println("文件中剩余字节数:"+input.available());
     }
          
          System.out.println(String.format("文件的大小:%d,缓冲区读取流返回的大小:%d",f.length(),bisLength));
      System.out.println("文件的内容："+strBuild.toString());
      System.out.println("字符串长度:"+strBuild.toString().length());
      char[] cTmp=strBuild.toString().toCharArray();
      System.out.println("字符串->字符数组长度:"+cTmp.length);

      end=System.currentTimeMillis();
      d=new Date();
      if(d!=null){ 
         d.setTime(end);
      }
      System.out.println("程序执行的结束时间:"+sdf.format(d));
      System.out.println("<-------------******************---------------->");
      System.out.println("程序执行时间(ms):"+(end-start)+"毫秒");

       }catch(FileNotFoundException ex){
          ex.printStackTrace();
       }catch(IOException ex){
          ex.printStackTrace();
       }finally{
         try{
               if(input!=null){
         input.close();
        }
           if(bis!=null){
         bis.close(); 
           }
         }catch(IOException ex){
           ex.printStackTrace();
         }
      }
   }
}

BufferedOutputStream类的例子如下：

import java.io.File;
import java.io.OutputStream;
import java.io.FileOutputStream;
import java.io.BufferedOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class BufferedOutputStreamDemo01{
        public static final int SIZE=1024;
        public static final String DRIVERNAME="oracle.jdbc.driver.OracleDriver";
        public static final String DBURL="jdbc:oracle:thin:@IP:1521:DB名称";
    public static final String USERNAME="用户名";
    public static final String PASSWORD="密码";
    
    static{
       try{
            // 加载驱动程序
            Class.forName(DRIVERNAME);
          }catch(ClassNotFoundException ex){
            ex.printStackTrace();
        }
    }

    public static void main(String[] args){
       // 变量声明
       File f=null;
       OutputStream output=null; 
       BufferedOutputStream bos=null;
           Connection con=null;
       PreparedStatement pst=null;
           ResultSet rs=null;
       StringBuilder strBuild=null;
 
           try{
          String sql=" select vendor_no,vendor_name,address,phone,email,zipcode from VENDOR";
           
          con=new BufferedOutputStreamDemo01().getConnection();
                  // 获得数据库操作类
                  pst=new BufferedOutputStreamDemo01().getPst(con,sql);
                  // 获得结果集
          rs=pst.executeQuery();

          f=new File("F:"+File.separator+"tmp.txt");
          output=new FileOutputStream(f,false);
          bos=new BufferedOutputStream(output,SIZE*4);
          
          while(rs.next()){
                        strBuild=new StringBuilder();
            
            // 店号
            strBuild.append(rs.getString("vendor_no"));
            strBuild.append(",");

                        // 店名
            strBuild.append(rs.getString("vendor_name"));
            strBuild.append(",");
            
            // 地址
            strBuild.append(rs.getString("address"));
            strBuild.append(",");
            
            // 电话
            strBuild.append(rs.getString("phone"));
            strBuild.append(",");

                        // 邮件
            strBuild.append(rs.getString("email"));
            strBuild.append(",");

                        // 邮政编码
            strBuild.append(rs.getString("zipcode"));
            strBuild.append("
");
            
                        bos.write(strBuild.toString().getBytes("utf-8"));
          }

           }catch(IOException ex1){
               ex1.printStackTrace();
       }catch(SQLException ex){
           ex.printStackTrace();
       }finally{
               try{
             // 关闭流
             if(output!=null){
               output.close(); 
             }
             if(bos!=null){
                            bos.close();
             } 
             //关闭数据库连接
             if(rs!=null){
                            rs.close();
             }
                         if(pst!=null){
                            pst.close();
             }
                         if(con!=null){
               con.close();
             }
                 }catch(IOException ex){
                ex.printStackTrace();
                 }catch(SQLException ex){
                    ex.printStackTrace();
             }
         }
    }
    
    /**
        **获得数据库连接
    **
    **/
    public static Connection getConnection(){
       Connection con=null;
       try{
           // 获得数据库连接
           con=DriverManager.getConnection(DBURL,USERNAME,PASSWORD);
       }catch(SQLException ex){
           ex.printStackTrace();
       } 

       return con;
    }
    
    /**
        **获得数据库操作类
    **/
    public static PreparedStatement getPst(Connection con,String sql){
            PreparedStatement pst=null;
        try{
          pst=con.prepareStatement(sql);
           }catch(SQLException ex){
          ex.printStackTrace();
           } 

        return pst;
    }
}