java输入输出

1、

import java.io.*;
//写进文档，然后又在显示器显示出来。
public class fileinputstream{
public static void main(String[] args) throws IOException {
DataOutputStream out = new DataOutputStream(new FileOutputStream("dest.txt"));
//定义要保存的数据数组。
double[] prices = { 19.99, 9.99, 15.99 };
//将prices中的数据以Tab键为分割符保存在文件中。
for (int i = 0; i < prices.length; i ++) {
out.writeDouble(prices[i]);
out.writeChar('\t');
}
//*********Found********
out.close();
// 创建数据输入流，将上面保存的文件再次打开并读取。
DataInputStream in = new DataInputStream(new FileInputStream("dest.txt"));
double price;
double total = 0.0;
for (int i = 0; i < prices.length; i ++) {
//*********Found********
price = in.readDouble();
in.readChar(); // 扔掉tab键
total = total + price;
}
System.out.println("For a TOTAL of: $" + total);
in.close();
}
}

2、

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
//把source.txt文件的内容复制到dest.txt内容

public class fileinput2{
public static void main(String[] args) throws IOException{
File inputFile;
File outputFile;
FileInputStream in;
FileOutputStream out;
int c;
inputFile = new File("source.txt");
outputFile = new File("dest.txt");
in = new FileInputStream(inputFile);
//*********Found********
out=new FileOutputStream(outputFile);
while ((c = in.read()) != -1)
//*********Found********
out.write(c);
in.close();
out.close();
}
}

3、

import java.io.*;
public class fileinput3 {
public static void main(String[] args) {
char[] charArray = {'a','b','c','d','e','f','g','h','i'};
char c ;
try{
//*********Found********** 文件流和数据输出流有什么区别
DataOutputStream out = new DataOutputStream(
new FileOutputStream("test.dat"));
for(int i =0; i<charArray.length; i++){
out.writeChar(charArray[i]);
}
//写进了文件，又读出来。
out.close();
DataInputStream in = new DataInputStream(
//*********Found**********
new FileInputStream("test.dat"));
while(in.available() != 0){
c=in.readChar();
System.out.print(c+" ");
}
System.out.println();
//*********Found**********
in.close();
}catch(IOException e){}
}
}

4、

import java.io.*;
public class fileinput4{
public static void main(String[] args){
int[] intArray = {1,2,3,4,5};
int j ;
try{
DataOutputStream out = new DataOutputStream(
new FileOutputStream("data.dat"));
for(j =0; j<intArray.length; j++){
//*********Found********
out.writeInt(intArray[j]);
}
out.close();

DataInputStream in = new DataInputStream(
//*********Found********
new FileInputStream("data.dat"));
while(in.available() != 0)
{
j = in.readInt();
System.out.println(j);
}
in.close();
}
catch(IOException e){}
}
}

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总结：一个是FileOutputStream 与FileInputStream

        另外一个是DataOutputStream与DataInputStream

5、文件输入输出一个实例

package lipika;

import java.io.*;

public class main {

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

    //获得两个文件类

    File inputFile = new File("c:\\test1.txt");

    File outputFile = new File("c:\\test2.txt");

    FileReader in = new FileReader(inputFile);    //创建文件读入类

    FileWriter out = new FileWriter(outputFile); //创建文件写出类

    int c;

    //如果到了文件尾，read()方法返回的数字是-1

    while ((c = in.read()) != -1) out.write(c);   //使用write()方法向文件写入信息

    in.close();     //关闭文件读入类

    out.close();    //关闭文件写出类

}

}

6、写一些数字到一个文本里面

package lipika;

import java.io.*;

public class main {

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

 

    File outputFile = new File("c:\\test2.txt");
    FileWriter out = new FileWriter(outputFile); //创建文件写出类
 
 for(int i=10000000;i<=10031893;i++){
  out.write(i + "\r\n");   //使用write()方法向文件写入信息  
 }
 out.close();
}   
}

7、

package lipika;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
public class youhuiquan  {
 public static void main(String[] args) throws IOException {
  File file=new File("c:\\test2.txt");
  FileInputStream fis=null;
  Scanner input=null;
  String str="INSERT INTO coupon(promoRuleId,couponNo,isSent,remainedTimes,STATUS,VERSION)"
    + "VALUES(37,123456789,0,1,1,0);";
  
  
   fis=new FileInputStream(file);
   input=new Scanner (fis);   
 
 
  StringBuffer nr=new StringBuffer();
   File outputFile = new File("c:\\test5.txt");
   FileWriter out = new FileWriter(outputFile); //创建文件写出类
  while(input.hasNext())
  {
   String hn = input.next();  
    out.write(str.replace("123456789", hn)+ "\r\n");   //使用write()方法向文件写入信息  
  }
   
   out.close();
  }   
  

  }