BufferedInputStream与BufferedOutputStream用法简介

Posted 2020-10-17 那啥快看

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：

 1 import java.io.File;
 2 import java.io.InputStream;
 3 import java.io.FileInputStream;
 4 import java.io.BufferedInputStream;
 5 import java.io.FileNotFoundException;
 6 import java.io.IOException;
 7 import java.text.SimpleDateFormat;
 8 import java.util.Date;
 9 
10 public class BufferedInputStreamDemo01{
11 
12     // 声明常量
13         public static final int SIZE=1024;
14 
15     public static void main(String[] args){
16        //变量声明
17            File f=null;
18        InputStream input=null;
19        BufferedInputStream bis=null;
20            StringBuilder strBuild=null;
21        SimpleDateFormat sdf=null;
22        Date d=null;
23            long start=0L;
24        long end=0L; 
25 
26           try{
27           sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
28           
29           strBuild=new StringBuilder();
30                   start=System.currentTimeMillis();
31           d=new Date();
32           if(d!=null){
33                   d.setTime(start);
34          }
35           System.out.println("程序开始执行时间:"+sdf.format(d));
36 
37       f=new File("d:"+File.separator+"demo.txt");
38           input=new FileInputStream(f);
39           // 指定文件带缓冲区的读取流且指定缓冲区大小为2KB
40       bis=new BufferedInputStream(input,2*SIZE);
41           int bisLength=bis.available();
42           int readLength=0;
43           byte[] byteArray=new byte[SIZE];
44           int tmp=0;
45           while((tmp=bis.read(byteArray))!=-1){ 
46                 strBuild.append(new String(byteArray,0,tmp));
47         System.out.println("每次读取字节数量:"+tmp);
48         System.out.println("文件中剩余字节数:"+input.available());
49      }
50           
51           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));
52       System.out.println("文件的内容："+strBuild.toString());
53       System.out.println("字符串长度:"+strBuild.toString().length());
54       char[] cTmp=strBuild.toString().toCharArray();
55       System.out.println("字符串->字符数组长度:"+cTmp.length);
56 
57       end=System.currentTimeMillis();
58       d=new Date();
59       if(d!=null){ 
60          d.setTime(end);
61       }
62       System.out.println("程序执行的结束时间:"+sdf.format(d));
63       System.out.println("<-------------******************---------------->");
64       System.out.println("程序执行时间(ms):"+(end-start)+"毫秒");
65 
66        }catch(FileNotFoundException ex){
67           ex.printStackTrace();
68        }catch(IOException ex){
69           ex.printStackTrace();
70        }finally{
71          try{
72                if(input!=null){
73          input.close();
74         }
75            if(bis!=null){
76          bis.close(); 
77            }
78          }catch(IOException ex){
79            ex.printStackTrace();
80          }
81       }
82    }
83 }

BufferedOutputStream类的例子如下：

  1 import java.io.File;
  2 import java.io.OutputStream;
  3 import java.io.FileOutputStream;
  4 import java.io.BufferedOutputStream;
  5 import java.io.FileNotFoundException;
  6 import java.io.IOException;
  7 import java.sql.Connection;
  8 import java.sql.DriverManager;
  9 import java.sql.PreparedStatement;
 10 import java.sql.ResultSet;
 11 import java.sql.SQLException;
 12 
 13 public class BufferedOutputStreamDemo01{
 14         public static final int SIZE=1024;
 15         public static final String DRIVERNAME="oracle.jdbc.driver.OracleDriver";
 16         public static final String DBURL="jdbc:oracle:thin:@IP:1521:DB名称";
 17     public static final String USERNAME="用户名";
 18     public static final String PASSWORD="密码";
 19     
 20     static{
 21        try{
 22             // 加载驱动程序
 23             Class.forName(DRIVERNAME);
 24           }catch(ClassNotFoundException ex){
 25             ex.printStackTrace();
 26         }
 27     }
 28 
 29     public static void main(String[] args){
 30        // 变量声明
 31        File f=null;
 32        OutputStream output=null; 
 33        BufferedOutputStream bos=null;
 34            Connection con=null;
 35        PreparedStatement pst=null;
 36            ResultSet rs=null;
 37        StringBuilder strBuild=null;
 38  
 39            try{
 40           String sql=" select vendor_no,vendor_name,address,phone,email,zipcode from VENDOR";
 41            
 42           con=new BufferedOutputStreamDemo01().getConnection();
 43                   // 获得数据库操作类
 44                   pst=new BufferedOutputStreamDemo01().getPst(con,sql);
 45                   // 获得结果集
 46           rs=pst.executeQuery();
 47 
 48           f=new File("F:"+File.separator+"tmp.txt");
 49           output=new FileOutputStream(f,false);
 50           bos=new BufferedOutputStream(output,SIZE*4);
 51           
 52           while(rs.next()){
 53                         strBuild=new StringBuilder();
 54             
 55             // 店号
 56             strBuild.append(rs.getString("vendor_no"));
 57             strBuild.append(",");
 58 
 59                         // 店名
 60             strBuild.append(rs.getString("vendor_name"));
 61             strBuild.append(",");
 62             
 63             // 地址
 64             strBuild.append(rs.getString("address"));
 65             strBuild.append(",");
 66             
 67             // 电话
 68             strBuild.append(rs.getString("phone"));
 69             strBuild.append(",");
 70 
 71                         // 邮件
 72             strBuild.append(rs.getString("email"));
 73             strBuild.append(",");
 74 
 75                         // 邮政编码
 76             strBuild.append(rs.getString("zipcode"));
 77             strBuild.append("\n");
 78             
 79                         bos.write(strBuild.toString().getBytes("utf-8"));
 80           }
 81 
 82            }catch(IOException ex1){
 83                ex1.printStackTrace();
 84        }catch(SQLException ex){
 85            ex.printStackTrace();
 86        }finally{
 87                try{
 88              // 关闭流
 89              if(output!=null){
 90                output.close(); 
 91              }
 92              if(bos!=null){
 93                             bos.close();
 94              } 
 95              //关闭数据库连接
 96              if(rs!=null){
 97                             rs.close();
 98              }
 99                          if(pst!=null){
100                             pst.close();
101              }
102                          if(con!=null){
103                con.close();
104              }
105                  }catch(IOException ex){
106                 ex.printStackTrace();
107                  }catch(SQLException ex){
108                     ex.printStackTrace();
109              }
110          }
111     }
112     
113     /**
114         **获得数据库连接
115     **
116     **/
117     public static Connection getConnection(){
118        Connection con=null;
119        try{
120            // 获得数据库连接
121            con=DriverManager.getConnection(DBURL,USERNAME,PASSWORD);
122        }catch(SQLException ex){
123            ex.printStackTrace();
124        } 
125 
126        return con;
127     }
128     
129     /**
130         **获得数据库操作类
131     **/
132     public static PreparedStatement getPst(Connection con,String sql){
133             PreparedStatement pst=null;
134         try{
135           pst=con.prepareStatement(sql);
136            }catch(SQLException ex){
137           ex.printStackTrace();
138            } 
139 
140         return pst;
141     }
142 }