打开文件

打开文件import java.io.*;public class OpenFile{public static void main(String args[]) throws IOException{try{ //创建文件输入流对象FileInputStream rf = new FileInputStream("OpenFile.java");int n=512;byte buffer[] = new byte[n];while ((rf.read(buffer,0,n)!=-1) && (n>0)) //读取输入流{System.out.print(new String(buffer));}System.out.println();rf.close(); //关闭输入流}catch (IOException ioe){System.out.println(ioe);}catch (Exception e){System.out.println(e);}}}写入文件import java.io.*;public class Write1{public static void main(String args[]){try{System.out.print("Input: ");int count,n=512;byte buffer[] = new byte[n];count = System.in.read(buffer); //读取标准输入流FileOutputStream wf = new FileOutputStream("Write1.txt");//创建文件输出流对象wf.write(buffer,0,count); //写入输出流wf.close(); //关闭输出流System.out.println("Save to Write1.txt!");}catch (IOException ioe){System.out.println(ioe);}catch (Exception e){System.out.println(e);}}}更新文件import java.io.*;import java.util.Date;import java.text.SimpleDateFormat;public class UpdateFile{public static void main(String args[]) throws IOException{String fname = "Write1.txt"; //待复制的文件名String childdir = "backup"; //子目录名new UpdateFile().update(fname,childdir);}public void update(String fname,String childdir) throws IOException{File f1,f2,child;f1 = new File(fname); //当前目录中创建文件对象f1child = new File(childdir); //当前目录中创建文件对象childif (f1.exists()){if (!child.exists()) //child不存在时创建子目录child.mkdir();f2 = new File(child,fname); //在子目录child中创建文件f2if (!f2.exists() || //f2不存在时或存在但日期较早时f2.exists()&&(stModified() > stModified()))copy(f1,f2); //复制getinfo(f1);getinfo(child);}elseSystem.out.println(f1.getName()+" file not found!");}public void copy(File f1,File f2) throws IOException{ //创建文件输入流对象FileInputStream rf = new FileInputStream(f1);FileOutputStream wf = new FileOutputStream(f2);//创建文件输出流对象int count,n=512;byte buffer[] = new byte[n];count = rf.read(buffer,0,n); //读取输入流while (count != -1){wf.write(buffer,0,count); //写入输出流count = rf.read(buffer,0,n);}System.out.println("CopyFile "+f2.getName()+" !");rf.close(); //关闭输入流wf.close(); //关闭输出流}public static void getinfo(File f1) throws IOException{SimpleDateFormat sdf;sdf= new SimpleDateFormat("yyyy年MM月dd日hh时mm分");if (f1.isFile())System.out.println("<File>\t"+f1.getAbsolutePath()+"\t"+f1.length()+"\t"+sdf.format(new Date(stModified())));else{System.out.println("<Dir>\t"+f1.getAbsolutePath());File[] files = f1.listFiles();for (int i=0;i<files.length;i++)getinfo(files[i]);}}}Chap08 练习题一package pj2172209212;import java.io.*;/*** <p>Title: </p>** <p>Description: </p>** <p>Copyright: Copyright (c) 2011</p>** <p>Company: </p>** @author not attributable* @version 1.0*/public class Lx1 {public static void main(String[] args)throws IOException{try{ //创建文件输入流对象FileInputStream rf = new FileInputStream("D:\\2172209212 王砚\\pj2172209212\\1.txt");int count,n=10,num=0;byte buffer[] = new byte[n];while ((count=rf.read(buffer,0,n))!=-1) //读取输入流{ num++;FileOutputStream wf = new FileOutputStream("Write"+num+".txt");//创建文件输出流对象wf.write(buffer,0,count); //写入输出流wf.close(); //关闭输出流}System.out.println();rf.close(); //关闭输入流}catch (IOException ioe){System.out.println(ioe);}catch (Exception e){System.out.println(e);}}}练习题二见手写Chap05 类的设计1package example;/*** <p>Title: </p>** <p>Description: </p>* <p>Copyright: Copyright (c) 2005</p> ** <p>Company: </p>** @author not attributable* @version 1.0*/public class Pg0501 {private int num; //被分解的数private int s[];private int count; //public Pg0501(int n){//?setNum(n);}public void setNum(int n){//?num=n;//分解过程if (num<2){s=new int[0];count=0;return;}int i=2;int t=num;int k=0;while (i<=t){if (t%i==0){++k;t/=i;}else{++i;}}s=new int[k];count=k;i=2;t=num;k=0;while (i<=t){if (t%i==0){s[k]=i;++k;t/=i;}else{++i;}}}public String toString(){//??String temp="";temp+=num;temp+="=";int i;for(i=0; i<s.length-1; ++i){temp+=s[i];temp+="*";}temp+=s[i];return temp;}public int getCount(){return count;}}类的设计2/*** Copyright(C) 2010 XXX.* 项目名称：* XXX* 模块概述：* 单词分解类* 备注：* 在简单进行程序设计的情况下，单词分解可能是一个很简单的问题，如"Copyright(C) 2010 XXX."这一句话分解的结果是"Copyright"、"C"、"2010"、"XXX"共四个单词，如果用程序来表达，可能就是下面的一段代码：public class analyzer{public static void main(String[] args){String sentence; //原始句子String separator=" ,;''"; //分隔符int i, j;i=0;while(i<sentence.length()) //循环流程：跳过连续的分隔符，取出一个单词{if (separator.indexOf(sentence.charAt(i))>=0) {++i; continue;} //跳过连续的分隔符j=i; //当前字符一定是一个单词的开始while (i<sentence.length() && separator.indexOf(sentence.charAt(i))==-1) ++i; //跳过单词到下一个分隔符或者字符串结束System.out.println(sentence.substring(j,i)); //取出一个单词}}}* 上述代码中有效的内容不过10行左右，但是这样进行程序设计，仅仅是完成了一次查找和输出过程，不仅可能没有完成任务，甚至是做了无用功，难于满足使用者（程序员）的要求，因而可复用的价值很低。