java中文件操作

例一：从一个文件读入数据，然后写入另外一个文件

package lipika;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class iofile {
public static void main (String[] arg ) throws IOException{
    FileInputStream f = new FileInputStream("c:\123.txt");
    byte[] dw =new byte [f.available()];
    f.read(dw);
    FileOutputStream d = new FileOutputStream("c:\456.txt");
d.write(dw);
System.out.print(d);
}
}

例二：生成150个随机数，写入文件当中

package lipika;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Random;


public class yhq {
    public static void main(String[] args) throws IOException{

    File outputFile = new File("c:\test3.txt"); 
    FileWriter out = new FileWriter(outputFile);
    
   
    //生成随机函数
    for(int i=0;i<150;i++){
        int number = new Random().nextInt(8999) + 1000;
        String zuizhong=new String("sfj200"+number);
        out.write(zuizhong + "
");          

    }
    out.close();
}    

}

例三：读取文件的数字，一行一行的读取，把这个数字替换掉某一个字符串中的某个数字，然后把新的字符串写入文件中

package lipika;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
public class yhqdaoru  {
    public static void main(String[] args) throws IOException {
        File file=new File("c:\test3.txt");
        FileInputStream fis=null;
        Scanner input=null;
    String str="INSERT INTO coupon(promoRuleId,couponNo,isSent,remainedTimes,STATUS,VERSION)"
                + "VALUES(81,'123456789',0,1,1,0);";
    /*    String str="UPDATE coupon SET promoRuleId=79 WHERE couponNo='123456789';";    */
        
            fis=new FileInputStream(file);
            input=new Scanner (fis);            
    
    
        StringBuffer nr=new StringBuffer();
         File outputFile = new File("c:\test4.txt"); 
         FileWriter out = new FileWriter(outputFile); 
        while(input.hasNext())
        {
            String hn = input.next();        
                out.write(str.replace("123456789", hn)+ "
");   
        }
         out.flush();
            
            out.close();
        }    
        


  }

 例四：如何生成随机数，写入文件当中

package lipika;

import java.io.*;
import java.util.Random;

public class lipika {

public static void main(String[] args) throws IOException {

  

    File outputFile = new File("c:\test30.txt"); 
    FileWriter out = new FileWriter(outputFile); //�����ļ�д����
 
    /*for(int i=10031893;i<=10031963;i++){
        
        out.write(i + "
");   //ʹ��write()�������ļ�д����Ϣ   
    }*/
    //生成随机函数
    for(int i=0;i<10000;i++){
        /*int number = new Random().nextInt(100000000) + 1;
        String zuizhong=new String("yhq20"+number);
        out.write(zuizhong + "
");  */
    /* 实现方式一，生成100000000 1个亿到9亿9千万。。。的随机数*/        
        
        /*int number = new Random().nextInt(899999999)+100000000;
        //new Random().nextInt(899999999)应该是900000000等才会生成生成100000000 1个亿到9亿9千万
        out.write(number + "
");  
    */
        /*实现方式二，*/
        long Temp; //不能设定为int,必须设定为long
        //产生 1个亿到9亿9千万的随机数
        Temp=Math.round(Math.random()*899999999+100000000);
        out.write(Temp + "
");
        

    }
    out.close();
}    
}

例五：读取文件的某个数字，替换字符串（数据库用），然后写入新的文件

package lipika;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;


public class lipikadaoru {

    public static void main(String[] args) throws IOException {
        File file=new File("E:\微信端30元1万张.txt");
        FileInputStream fis=null;
        Scanner input=null;
            String str="INSERT INTO gift_certificate ("
                    + "giftCertificateNo,purchaser,recipient,isSentByEmail,giftCertAmt,remainedAmt,giftType,STATUS,VERSION,"
+ "m1Amt,m2Amt,m3Amt,m4Amt,m5Amt,m6Amt,m7Amt,m8Amt,m9Amt,m10Amt,m11Amt,m12Amt,customerId,registerTime)"
                    + "VALUES('123456789','N/A','N/A',1,500,500,1,1,0,30,0,0,0,0,0,0,0,0,0,0,0,-2,'2014-10-09 14:00:00');"
                    ;
        try{
            fis=new FileInputStream(file);
            input=new Scanner (fis);
            
        }
        catch(IOException e){
            e.printStackTrace();
            
        }
        StringBuffer nr=new StringBuffer();
         File outputFile = new File("e:\test30.txt"); 
         FileWriter out = new FileWriter(outputFile);
        while(input.hasNext()){
            String hn = input.next();                
        
            out.write(str.replace("123456789", hn)+ "
");
            out.flush();
        }
        
                                      
    }

}