java_IO向文件中写入和读取内容代码实例

package stream;

import java.io.file;

import java.io.filenotfoundexception;

import java.io.fileoutputstream;

import java.io.ioexception;

import java.io.outputstream;

public class outstreamdemo01 {

     public static void main(string[] args) {

         //定义文件路径，没有该文件会自动创建，如果路径有文件夹，一定要有，不会自动创建文件夹

         string filename = "e:" +file.separator+ "a" +file.separator+ "b.txt" ;

         file file = new file(filename);

         string str = "这些都将写入文件中" ;

         byte [] b = str.getbytes();  //将字符串转换成字节数

         outputstream out = null ;

         try {

             out = new fileoutputstream(file);   //实例化outpurstream

         } catch (filenotfoundexception e){

             e.printstacktrace();

         }

         //写入

         try {

             out.write(b);       //写入

             out.close();        //关闭

         } catch (ioexception e) {

             // todo auto-generated catch block

             e.printstacktrace();

         }

     }

}

package stream;

import java.io.*;;

public class inputstreamdemo01 {

     public static void main(string[] args) {

         file file = new file( "e:" +file.separator+ "a" +file.separator+ "b.txt" );

         byte [] b = new byte [( int )file.length()]; //定义byte字节的长度

         inputstream in = null ;

         int len = 0 ;

         try {       //处理异常

             in = new fileinputstream(file);     //实例化fileinputstream类

         } catch (filenotfoundexception e) {

             // todo auto-generated catch block

             e.printstacktrace();        //输出异常

         }

         try {

             len = in.read(b);       //读取指定文件的内容

             in.close();

         } catch (ioexception e) {

             // todo auto-generated catch block

             e.printstacktrace();

         }

         system.out.println( new string(b, 0 ,len)); //将字节数组转化成字符串输出指定文件从0开始到len字节结束

     }

}