copyfile.java

Java学习源代码检索系统免费版

//==============================================================
// CopyFile.java - Demonstrates file stream input and output
//
// Java学习源代码检索系统 Ver 1.0 20031015 免费正式版
// 版权所有: 中国IT认证实验室(www.ChinaITLab.com)
// 程序制作: ChinaITLab网校教研中心
// 主页地址: www.ChinaITLab.com    中国IT认证实验室
// 论坛地址: bbs.chinaitlab.com  
// 电子邮件: [e-mail]
//==============================================================

import java.io.*;

public class CopyFile {
 
 // Input a string
 public static String readLine()
  throws IOException {
  BufferedReader br = 
   new BufferedReader(new InputStreamReader(System.in));
  return br.readLine();
 }

 // Prompt for and input a string
 public static String readLine(String prompt)
  throws IOException {
  System.out.print(prompt);
  return readLine();
 }

 // Construct File object for named file
 public static File getFileForFilename(
  String filename, boolean checkExistence)
  throws IOException {
  File fi = new File(filename);
  if (checkExistence) {
   // Do not move the following statements;
   // order is critical
   if (!fi.exists())
    throw new IOException(fi.getName() + " not found");
   if (!fi.isFile())
    throw new IOException(fi.getName() + " is not a file");
  }
  return fi;
 }
 
 // Returns true if user answers yes to prompt 
 public static boolean yes(String prompt)
  throws IOException {
  System.out.print(prompt);
  char ch = (char)System.in.read();
  if (ch == 'y' || ch == 'Y') {
   return true;
  }
  return false;
 }
 
 // Copy and old file to a new one
 // Overwrites or creates the new file
 public static void copy(File fileOld, File fileNew)
  throws IOException {
  FileInputStream fin = new FileInputStream(fileOld);
  FileOutputStream fout = new FileOutputStream(fileNew);
  System.out.println("Copying...");
  int b = fin.read();
  while (b != -1) {
   fout.write(b);
   b = fin.read();
  }
  System.out.println("Finished");
 }
 
 // Main program method
 public static void main(String args[]) {
  String fileOldName, fileNewName;
  File fileOld, fileNew;
  try {
   if (args.length >= 2) {
    fileOldName = args[0];
    fileNewName = args[1];
   } else {
    fileOldName = readLine("Copy what file? ");
    fileNewName = readLine("To what file? ");
   }
   fileOld = getFileForFilename(fileOldName, true);
   fileNew = getFileForFilename(fileNewName, false);
   if (fileNew.isDirectory())
    throw new IOException(
     fileNew.getName() + " is a directory");
   if (fileNew.exists()) {
    if (!yes("Overwrite file " + fileNew.getName() + "? "))
     throw new IOException("File not copied");
   } else {
    if (!yes("Create new " + fileNew.getPath() + "? "))
     throw new IOException("File not copied");
   }
   copy(fileOld, fileNew);
  } catch (IOException e) {            // Trap exception
   System.err.println(e.toString());   // Display error
  }
 }
}